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GMKindl, ASE Certified Technician
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Experience:  ASE Master Certified Techniciain, Advanced Engine Performance Specialist, GM Pro Service Guild
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50 to 60 miles per hour) there is a vibration..firewall..disappears

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When driving at 1,200 to 1,500 RPM (50 to 60 miles per hour) there is a vibration that seems to be in the floor board near transmission and firewall. Especially stays (vibration) when car is definitely at 1,500 RPMs. Once you let off gas, it disappears. It also feels like at 1500 rpms, that the car seems like it's going up a steep hill -- sounds like its struggling the engine!

2009 GMC Yukon XL 5.3 liter
Flex Fuel
Active Fuel Management
700 miles on Vehicle
Hello and welcome to Just Answer. How long have you been experiencing the concern? Does the Driver Information Center (DIC) display the engine mode (4cyl or 8cyl)? Do you have ANY modifications like exhaust or anything like that?
Customer: replied 7 years ago.
Have experienced the problem with the car from the second day after the car left the dealership. Only drove it home the first day (approx 5-7 miles). Starting driving longer distances the second day I had the car (ie highway at 60 miles) and noted it immediately.

Never looked at the DIC at the time of the problem.
How would I know? How do I find the mode while driving? I definitely will take note when it happens if I know what to do. I will be driving tomorrow on the highway.

I only know of a chrome tailpipe with the chrome package from GMC.

Ok, so it sounds like the vehicle is stock and has not been altered. Sometimes after-market, and even GM approved accessories, can cause concerns similar to yours. The DIC display sometimes will show you what mode the engine is in, usually this display is coupled with the fuel economy info. You should be able to find this by pressing the fuel and vehicle buttons that scroll through the trip odometer and such. You can set it to any of the displays to watch while driving. I am curious to know if the vibration you feel only occurs in the 4cyl mode. I have run into very similar concerns with owners of the new 2010 Camaro. The vibration and exhaust note change noticeably when the vehicle switches into 4cyl mode. After driving several of these cars and speaking with GM engineering, it was concluded that this was a normal operating carachteristic. So if your Yukon only experiences this in 4cyl mode, this may be a normal condition. You could double check this by taking a test drive in another Yukon with Active Fuel Management. If the comparison vehicle also exhibits this condition it is likely a normal characteristic. I also did a bulletin search for your vehicle and did fond one bulletin that may apply. You have very low miles, and it started on day 2 so it's an outside chance but still worth having the dealer check. I will post the bulletin below for you. If the vibration is noted try accelerating to get the engine to switch back into 8cyl mode to see if vibration diminishes.

Subject: Vibration Felt and Heard During Low RPM Driving - Inspect for Trans Mount Debris
Models:2004-2007 Buick Rainier
2001-2009 Cadillac Escalade
2002-2009 Chevrolet Trailblazer and Trailblazer EXT
1999-2009 Chevrolet Avalanche, Silverado, Suburban, Tahoe
1999-2009 GMC Sierra, Yukon
2002-2009 GMC Envoy, Envoy XUV and Envoy XL
2003-2009 Hummer H2
2002-2004 Oldsmobile Bravada
2005-2008 Saab 97x

This PI was superseded to include Full Size Trucks and Utilities. Please discard PIT3516C.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


An unusual vibration may be felt and heard at very low RPM, especially during parking lot maneuvers or driving at lower speeds and making a gradual left or right turn. A rattle may also be heard from under the vehicle that can be felt in the floor as the engine is started due to Powertrain movement. If equipped, this may be more pronounced when AFM (Active Fuel Management) is active.

This may be due to stones and debris being trapped in the transmission mount as shown below, which may transmit the noise/vibration into the body.

Example of a 2008 Silverado Shown Here

Object Number:(NNN) NNN-NNNN Size: SH


If SI diagnosis does not isolate the cause of this concern, remove the transmission mount and clean the debris out of the mount. Then install a 5.5" (14cm) section of 0.75" (19mm) heater hose into the cavity of the transmission mount to prevent debris from entering the mount as shown below, reinstall the mount, and re-evaluate the concern.

Notice: There should be no need to replace the mount when this issue is encountered.

Example of a 2008 Silverado Shown Here.

Object Number:(NNN) NNN-NNNN Size: SH

Object Number:(NNN) NNN-NNNN Size: SH
Customer: replied 7 years ago.
I will check the DIC and get back to you.

Secondly, I just came out of a 2007 Surburban with the same engine -- and absolutely no noise and no vibration.

What is different then? What was changed?
Why would one car have and yet not another with the same engine?
What can be done to have this vehicle feel and sound the same as the other vehicle with the same engine?

The noise in the Yukon never leaves at 1500 rpms. I will check the cylinders tomorrow.

And if I find that it is in 4 cylinders only when the noise and vibration come, what can I do at that point to stop it?

How do I get back in touch with you tomorrow night? I get home late.

I appreciate your time and will like to get this resolved.
I will check back again tomorrow, late as well. I will be home around 9:30 or 10:00 pm central time. The differences bewteen the trucks may include a difference in gearing, a 4speed trans in the Suburban, and a 6speed trans in the Yukon. Even just a difference in engine calibrations could explain the difference in vehicles. If you find that the noise occurs in 4cyl mode then I would try to compare to another vehicle. If the same noise is in the other vehicle then I would say it's a normal operating carachteristic and there is no fix at this time. That does not mean that there could not be a fix in the future. Most likely a concern like this is corrected with simple calibration change (reprogramming the engine control module). If it does appear to be normal but the noise is undesireable to you, your dealer needs to file a field product report. This report goes straight to GM brand quality engineers for review, with enough reports they will then address this concern. Kind of the squeaky wheel getting the grease, if you know what I mean. I will continue to follow this post and if you have further questions and info just post here.
Customer: replied 7 years ago.

Talk to you tomorrow
Customer: replied 7 years ago.
As you suggested, took car for usual travel for work and checked the DIC and it said economy and mode 8 cylinder at the start. Then I drove at 1200 rpms and it was still in 8 cylinder mode and the noise started. Drove 1500 rpms steady and car was still in 8 cylinder. It never changed. Vibration is very evident and the noise sounds like a hole in the muffler entering the car or a lawn mower running underneath the vehicle.

The ONLY time the car went into 4 cylinder mode was when I released the gas -- coasting with foot off the gas pedal -- and there was no noise and no vibration in the car.

Now, when I accelerated from 1200 rpms to 2000 rpms, the noise got very very loud and the vibration was steady.

It actually overwhelmed the radio and all I could hear was the noise as the engine was vibrating.

Very scary and very unsettling as the noise is very annoying but I no longer felt safe in the car.

So different than what was originally expected and what we discussed yesterday.

But one thing I noticed, that as the car runs longer and gets hotter, the noise gets louder.

Now what??? Please help!

P.S. I repeated this process, 3 times today to demonstrate repetitive problem.
Ok. So it does not seem like its a normal noise. There are a few things we can do to narrow down which area of the vehicle that may be causing the noise. Most of these things will require an area where you can drive the vehicle in a safe place, preferably a large empty parking lot. Do you have a space where you can drive it and do some testing? Does the noise only happen above a certian mph? I know you said it was engine speed related, is the noise present at low speeds when the engine is at 1200-2000 rpm? Is your Yukon 2wd or 4wd? By all means if you do not feel safe driving the vehicle then have the dealer tow it back to the shop so they can fix it for you. I am glad to help narrow it down for you by doing some simple testing if you would like though.
Customer: replied 7 years ago.
I do hear some noise at 25 to 35 mph but not loud. It is worse at 60 mph. The noise takes over the cabin. The only time the noise and vibration is gone is when I take my foot off the gas pedal.

This Yukon is 2wd.

I would like to do some testing with you -- since the dealership service advisor thought it was maybe A/C lines rubbing near the accumulator and re-routed lines for clearance. I brought it back again a second time and they heard the noise again but the second time they thought it was exhaust out of alignment? and made some adjustments -- but it is worse now than ever.

When the dealership service test, they drive for only a mile or two. I am driving for over 45 minutes.

I would like to try your testing with you.

Please advise.
Sure, I will be glad to help try and get the problem isolated for you. So the first thing to do is rather easy. Drive the truck up to the speed at which the noise is present, then shift the transmission into nuetral. Of course you are going to have to let off the gas, as to not over rev the engine. Is the noise still present? If it is no longer present then the noise is related to the engine. You may have to try this a few times to get a handle on the effect. If the noise is still present shift back into drive and try applying the brakes very lightly while driving at that same speed, you will likely have to put one foot on the accelerator and one on the brake to accomplish this. One other thing to try is and turn on some of the accessories, like a/c , maybe even the wipers, just anything that may get the noise to change is what we are looking for here. The last thing to try is to drive the vehicle to the noise speed, and then shift the transmission into nuetral, and then turn the ignition off. I can NOT stress enough to make sure you do this in a safe place. DO NOT do this on the freeway or in busy traffic. One more thought that just came to mind, does the Yukon have a bug shield installed? If so try removing it and see if the noise is present. Most of the newer trucks have 4 screws holding the bug shield on.
Customer: replied 7 years ago.
OK will test tomorrow Tuesday and get back to you!
Sounds good.
Customer: replied 7 years ago.
I did what you asked of me.

1. I drove the car 1200 - 1500 rpms and kept my foot on the pedal 45-50 mph and then dropped it into Neutral gear...

the noise seemed to lessen and dissipate and even the vibration seemed to lessen -- but it was hard to do both: keep the foot where the noise and vibration is and drop it into neutral.

Engine is still running at high rpm.

I did this at 1500 to 1600 rpm = VERY noisy at that rpm.

I let off gas as soon as I dropped to neutral and the same seemed to happen -- the noise and vibration in cabin seemed to lessen.

(RPM is racing when I drop into neutral as engine is running)

2. I did what you asked and drove at the LOUDEST NOISE & VIBRATION and kept foot on gas and gradually applied the brakes: NOISE and VIBRATION NEVER went away!

I was at 62 mph on gas pedal and braked lightly to 45 and NOISE never left and VIBRATION never left car.

3. Ran car to 1200 where nosie starts and dropped to neutral and shut off engine: NO NOISE & NO VIBRATION!

NOTE: I did #1 eight to ten times and #2 at least six times and #3 two times.

Now the noise and vibration are even with local driving every time the car hits that 1100 to 1200 rpm. She vibrates and this noise starts in the cabin especially.

NOISY at 1500 to 1600 rpm and every time the noise in in the car it is in 8 cylinder mode.

The only time this car has no vibration and no noise is when you are coasting off the gas.

Once you hit the gas pedal -- here comes the vibration and the noise!

Noise and Vibration at its worse 1000 to 1600 rpm steady driving -- engine at that time sounds like I am going up a mountain and engine is struggling.

We are on the right track right? This is NOT normal!

Please help!

P.S. Put the air conditioner on as you suggested and the noise and vibration did not change.
You did a good job testing things today. Just to sumarize your tests, it seems as if the noise/vibration is always present with the engine running at cruise speeds (1200-1600 RPM). Right? And if you turn the engine off with the key, the noise is no longer present? And as long as the engine was running (and not coasting) nothing you seem to do made a change in the noise/vibration? If my assumptions are correct, then we have isolated the source of the noise to the engine. Is this accurate?
Customer: replied 7 years ago.
The noise and vibration are only gone when I am coasting and when the engine is off.

So what needs to be done to get this fixed?
Ok. That's what I thought. Let me do a little searching and I will get back to you. It may take me up to an hour but I will post here when I either have more questions for you or have a possible solution, Ok?
Customer: replied 7 years ago.

Hope you can help.

You're the doctor with the patient.

Need a resolution and fix!

You're the expert.
Thank you.
I will do my very best to get this figured out for you. A couple quick questions. Does the engine seem to run well otherwise? Smooth idle? Good power? And secondly; would you mind posting the last 8 digits of the VIN # XXXXX I can look at the specific build of your Yukon?
Customer: replied 7 years ago.
When I was testing for you today -- I noticed as I was coming to the light and braking, there was a little downshift or hold back.

The engine races on rpms when I am on the ramp picking up speed to gain entrance to a highway.

When I am stopping at the light, there is sometimes a rough idle. I can feel it in the seat.

When I am in park, the car seems smooth idle.

On take off, ie red light turns green, there is a little jump or kick and not as smooth as it could be.

Also, when I come to a red light to brake, a little downshift seemed to occur while I am still just braking to stop.

The power after 1800 -- excessive speed -- seems ok but the wind factor on the car overpowers the noise and the vibration is still felt.

I took it to the dealer the first time for the noise/vibration and a hesitation when taking off -- they just re-routed A/C lines and said needs ECM update as for doc 4112H and performed ECM update code C11757.

The last 8 Digits of this Yukon is: 9R283568

Please find the remedy!
Thank You for that info. I am searching Gm service information as we speak and will get back to you soon.
Customer: replied 7 years ago.
Thank you.
Ok. So I have looked over GM service information and am not finding a lot that is sticking out. I did find a couple of service bulletins that relate to exhaust noises. I am not real sure that is the source of your noise but it is definitely worth looking into. The first of the two bulletins talks about a heat shield that is strapped onto the muffler. According to the buletin the straps could be slightly loose allowing the shield to rattle and cause a noise. The bulletin tells us to install some shims to temporarily tighten the strap and then drive the vehicle...if the noise is gone then replacing the straps will cure the noise. If the noise is still present then the shield is not the source of the noise. The second bulletin talks about a exhaust pipe joint that would be located under the passenger section of the vehicle. It looks like that joint may be mis-aligned and could cause an exhaust leak. If a leak is present then the clamp around the joint needs replacing, this should cure the leak and noise. I will post both bulletins for your reference at the end of this post. Other than these two things I am not finding a lot of solutions to your vibration/noise. I did see that your Yukon isXXXXXby the build data I was able to access. You might try making sure the selector switch is in 2wd and not in 4wd. Or even see if the noise changes by changing from 2wd to 4wd or vice versa. On the chevy models this switch is on the left side of the steering wheel near the light switch. This switch is easily bumped when entering and exiting the vehicle. One of the next things I would do as technician working on thios vehicle after isolating the noise to the engine would be to remove the serpentine accessory drive belt to make sure the noise was not a bolt on accessory (power steering pump, water pump, alternator, etc..). I would advise having a trained technician do this due to the possibility of needing spceial tools and making certian proper belt routing when reinstalling the belt. The engine can not be run too long with out the belt due to the water pump no longer being driven. Most of the things as far as repair goes will point you back at the dealer for the repair. I know previously they have not fixed the vehicle for you but maybe I can suggest a few things that will make that process a little easier and more successfull. First ask for the technician who will be repairing your vehicle to go for a test drive with you. You may even want him to drive so that he feels and hears the vibration from the drivers perspective. This way he knows specifically which noise/vibration that you have concerns with. I do this as much as possible in noise/vibration concerns. If he can not get the noise/vibration to happen asl if you can drive to see if you can get it to act up. This also gives the technician a chance to ask any specific questions he may have. No need for a long test drive just long enoug to get the concern to happen. If the technician can not or will not go with you, ask for the servie manager to drive with you instead. If they say the noise is normal then ask them to show you by demonstrating the same noise in another new vehicle. If your dealer is not getting it done for you try any other GM dealer, they can all do warranty repairs on your Yukon. I wish I were able to nail down a solution for you, however I am a little handicapped by not being able to see, hear, and feel your noise/vibration. I do believe that it's not a normal noise and it needs repair. I know this whole process can be very frustrating, please remember that your dealer are not the people who built your truck. And that it is in thier best intrest to fix this for you.

Now the two bulletins I promised will follow.

Subject:V8 Engines -- Muffler Buzz During Vehicle Operation or Exhaust Popping/Snapping Noise (Normal Condition) When Vehicle is Hot, at Idle, or Immediately After Vehicle is Shut Off (Replace Straps on Muffler Heat Shield for Buzz Noise Only)
Models:2007-2009 Cadillac Escalade Hybrid, Escalade ESV, Escalade EXT

2007-2009 Chevrolet Avalanche, Silverado (New Body Style), Suburban, Tahoe Hybrid

2007-2009 GMC Sierra (New Body Style), Sierra Denali, Yukon, Yukon XL, Yukon Denali, Yukon Denali XL

Equipped with the following V8 Engines:

- 4.8L (RPO LY2)

- 5.3L (RPOs LC9, LH6, LMG, LY5)

- 6.0L (RPOs LFA, L76)

- 6.2L (RPOs L9H, L92)

Please Refer to GMVIS

This bulletin is being revised to apply only to vehicles equipped with V8 engines and remove GEN3 engines. Please discard Corporate Bulletin Number 07-06-05-001E (Section 06 -- Engine/Propulsion System).


Some customers may comment on a popping/snapping noise from underneath the vehicle at idle or immediately after the vehicle is shut off. Some popping/snapping noise from the exhaust system during cool down is a normal condition. The noise may be intermittent depending on the outside temperature and or temperature of the exhaust system at the time of testing.

Some customers may also comment on a buzz noise coming from the muffler during vehicle operation.


Exhaust Popping/Snapping:

As the exhaust system cools, the muffler shell and muffler internals contract at different rates. Some popping/snapping noise from the exhaust system during cool down is a normal condition.

Muffler Buzz:

If the muffler heat shield straps are loose, the heat shield may be free to buzz.



Exhaust Popping/Snapping Noise:

This condition is normal to the muffler design and does not indicate poor quality or part failure.

Muffler Buzz:

Confirm the origin of the buzz by shimming (use metal shims) the straps tight and rerunning the vehicle. If the buzz concern is gone, then it is caused by the loose shield. Using the following procedure, install new straps to secure the heat shield to the muffler.

  1. Install three straps, P/N 10391259, so that the strap screw head will be located on top of the muffler.
  2. Tighten
    Tighten the strap screw to 4 N·m (35 lb in).

  3. Cut off the excess strap material and bend the strap over the strap screw head.

Parts Information

Part Number




Strap, Exhaust Muffler Heat Shield


Warranty Information

For vehicles repaired for a muffler buzz, use the following labor operation:

Labor Operation


Labor Time


Strap, Muffler Heat Shield - Replace

0.3 hr

*This is a unique labor operation number for bulletin use only. It will not be published in the Labor Time Guide.

And the second....

Subject:Exhaust Leak/Noise At Band Clamp
Models:2009 Chevrolet Avalanche, Silverado, Suburban, Tahoe

2009 GMC Sierra, Yukon, Yukon XL

1500 Models With 4.3L, 4.8L, 5.3L, or 6.0L Engine

This PI was superseded to update the repair information. Please discard PIT4859.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


Some owners may comment of an exhaust leak or noise. This concern could be caused by an unseated pipe to pipe mid joint connection, as shown below.

Object Number:(NNN) NNN-NNNN Size: SH


To correct this concern, replace the band clamp and push the pipes together while tightening the clamp bolt. The pipe flares must be seated while tightening the clamp. After clamp is installed it does not need to be perpendicular to the pipe. It is acceptable to have a pipe to pipe or clamp angle. Confirm that the clamp edges (both sides and all the way around the clamp) are seated on the pipe, as show below.

Object Number:(NNN) NNN-NNNN Size: SH

Customer: replied 7 years ago.

So today I took a trip to the dealership where I purchased my vehicle and explained about the noise and vibration and how it is getting worse.

As you advised, I asked the service mechanic and the service manager to ride with me and drive the car. They admitted they could hear the noise and feel the vibration. I sat in the back sit and could hear and feel under my feet (first time I drove in the back).

The tech sitting on the passenger side was asked by the service manager who was driving what he thought it could be. The tech said it was in the exhaust and maybe residue or something like that.

But then when we got back to the dealership, the service manager spoke to the sales rep and suddenly came back and notified me the noise was normal.

Then I showed him the bulletins you gave me and they refused to even put the car on the lift to check it out!

Then as per your advice, I demanded to drive another 2009 identical vehicle and the tech said I needed to add gas -- but the service manager indicated he wanted to drive and only needed enough gas for a mile to two. He did not take the service tech with us. I insisted to drive but could not get too far with so little gas and the low fuel indicator -- but there was no noise or vibration. The car was not even hot when we had to come back.

So when I said see how different this car rides with no noise from my car -- the service manager said nothing. But when we went back to the sales manager who sold me the car, I told him this car is completely different ride than mine but the service manager when asked said the noise and vibration was just like mine!

I refuted that and asked that since the exhaust was maybe a factor, could they at least look at the bulletins and check out my car.

They refused!


See no evil - hear no evil - speak no evil.

They would not let me leave the car either.

I was SHOCKED!!! The car is over 58,000 dollars with a warranty and a problem that they refused to even check out.

SO I took your other advice and went to another GM dealership. The salesreps said it is not true what you told me and that I had to go back to where the car was purchased.

Fortunately, someone knew me there and talked the service into at least checking out my car. I reminded them I never purchased from them because they had nothing available to sell. They remembered but said they were not obligated to check the car.

At least they agreed finally and called the mechanic who took a ride with me. He heard the noise and told me to pull over and he opened the hood to find anything loose. Then he insisted on driving it back himself. Then he agreed to put it on the lift and I gave him your 2 bulletins and he agreed to check.

He reported back to me that he reviewed the bulletins you gave but found nothing even though he attempted to tighten what might have been loose but was not. The service rep actually said to me, the sound is like a growl -- like a beast in the exhaust waiting to get out!

At that point, he brought the car back to me and the service said although they hear the noise and it is NOT normal, they would need direction from GM or you as to what the fix is. Without direction what to do next, they would not do anything more.


Have you driven a Yukon 2009 XL 5.3 engine with 6 speed?

Could you do so at 1200 - 1500 rpms and let us know what the fix is!

PLEASE tell me there is a fix.

As you and the dealership services agree this is definitely not normal -- WHAT can be done to cure and fix!!!


I am willing to go anywhere to get this fix even if GM will not under the warranty -- which I am entitled to -- but I am also entitled to enjoy my new vehicle!

I am at a loss for words on what happened at the dealer for you today. I am researching a couple things and will have a full response in a few minutes.
Like I said I am at a loss for the way you were treated by the dealer that sold you your Yukon. I work for a moderate sized dealer in the midwest and can tell you that type of treatment is totally unacceptable. As a GM enthusiast, owner, and dealer employee I want to extend my apologies. Without loyal GM customers, like yourself, a lot of people would be without jobs, houses, and families. I am glad that the second dealer you took your truck to at least looked and listened to the noise. You can indeed have your truck worked on at ANY GM dealer. It is called cross-line warranty and I perform these repairs on a daily basis. I am copying a part of the GM dealer Policies and Procedures manual that highlights these repairs.

GM Service Policies and Procedures Manual

  1. 1 - ARTICLE 1
    1. 1.4 - Warranty Repairs, Special Coverage Adjustments, Policies on Specific Vehicles, Components and Programs
      1. 1.4.17 - Cross-Line Warranty

Cross-Line Warranty

Cross-line warranty allows GM and Saturn Service Agents to perform warranty repairs on:

  • Non-franchised vehicles requiring repairs under the GM warranty where customers are significantly inconvenienced and in need of those repairs
  • Non-franchised used vehicles sold by the selling Service Agent (including in-stock used vehicles requiring warranty repair)
  • Commercial vehicles (by designated GM commercial truck Service Agents)

First and foremost, one of the benefits of cross-line warranty is the ability to perform repairs for customers who are significantly inconvenienced. Service Agents should determine if:

  • They possess the necessary skills (training, tools and parts) before attempting any cross-line repair. The overall intent is to provide an opportunity for customer satisfaction in a potentially negative ownership experience.
  • Questions regarding a specific situation should be reviewed with your District Service Manager.

Cross-line warranty can be performed for used vehicles.

  • Any used GM vehicle resold by a GM Service Agent may obtain warranty service from the selling GM Service Agent regardless of the Service Agent's new vehicle franchise. This will be helpful to Service Agents who have sold a used vehicle to a customer that is different from their franchise and will not have to turn the customer away for any remaining warranty work.
  • Service Agents will need to make certain their Service team possesses the necessary skills (training, tools and parts) before attempting any cross-line repair.

Partial wind-down dealers can perform warranty service beyond their wind-down date on the brands they will no longer represent until the October 2010 expiration of the current Dealer Sales & Service Agreement.

Participation in cross-line warranty is voluntary. GM Service Agents and Saturn retailers are prohibited from promoting or advertising cross-line warranty repairs. Any violation of this could result in audit, Service Agent charge back or termination of cross-line capability. Repairs performed outside of the warranty are not eligible for cross-line warranty and require wholesale authorization.


As for the noise itself I am relieved to hear that it is initially thought to be an exhaust noise. That at least means that there is no immediate safety or security concern. I would have a look closer at the second bulletin I referenced earlier, I suspect maybe this could be the source of the noise. That service bulletin number is XXXXX If it turns out that is not the problem, the next step would be to have the technician contact GM Technical Assistance Center. The dealership should have the number to contact them. Technical Assistance will have a much larger database with similar concerns and their solutions than I have. I am also going to give you the phone number to GMC customer service (1-800-462-8782), you will need to continue to press 0 through all the automated prompts to get a service representative. Tell the rep of your concerns, how you were treated at the dealer who sold you the truck, and that your other dealer has agreed to look at it and continue repairs with GM assistance. Ask if they can help you get this fixed at the second dealer. I did spy a Yukon XL on our lot this afternoon, I will check on it tomorrow and see if I can get a drive in it. I hope you have much better luck tomorrow and I will again get back to you tomorrow night.
Customer: replied 7 years ago.
Your response was well appreciated. Reading your response, I just want to let you know that we own a small Mom/Pop business on Long Island and treat customers as you spoke you do. We deal with nickles and dimes with our customers and treat them that the customer comes first. One then tells another and our business is ok. Was totally shocked today. I would think they would want to keep me as a customer having bought 9 GM cars out of 11 years. So I Thank you for your sincere response.

Originally the first dealer who refuses to help me now -- told me that the AFM - Active Fuel Management -- is the problem and that there is no fix.

From the testing you had me do and from your responses, it is safe to assume that the AFM is not the issue?

The new dealer willing to assist did review both bulletins you gave and said they performed both -- but no improvement. They are suspecting the exhaust (calling it a beast trying to get out) -- and you seemed to also head in that direction of the exhaust.

Good luck driving the Yukon and you know the car needs to get warm.

P.S. Midwest is pretty far for me to drive my car to you!
Hope you find the fix!
I did find the Yukon today, but it's a 2007 and does not have the same engine and trans combinatin that your vehicle has. So I am sorry to report that I did not get a chance to drive a comparable vehicle today. I can indeed tell you that AFM does cause a change in the exhaust tone that you hear. AFM effectively turns your V8 into a V4 which I am sure you are aware of. From my experiences with the Camaro and noise/vibration concerns, I can tell you that GM engineering has tried to get the newer versions of AFM engines to operate in V4 mode more of the time. This is an active effort to improve the fuel economy of the vehicle. This is also a difference from your older 2007 Suburban with AFM. So I guess what I am saying is that it's possible that the noise/vibration is indeed a normal operating carachteristic. With that in mind what we can address to make your ride more enjoyable is trying to minimize the noise. The exhaust system has a natural resonance frequency, what engineers normally try to achieve is having that resonance frequency peak outside normal operating ranges. This way we rarely hear it. One way they accomplish this is to rubber mount the exhaust system. Rubber mounting helps reduce the resonance back into the cabin of the vehicle. So we need to make sure all of the rubber mounts are in tact, and properly adjusted. By properly adjusted I mean that all mounts are free moving and not touching (grounding out) to the body or frame they are mounted from. If the one of the mounts is grounded out it allows a path for the resonance to transfer to the cabin of the vehicle. Secondly we need to check and see if your exhaust has a flex joint in the pipe. A flex joint is a short section (6 to 12 inches) of a stainless steel mesh pipe. What this type of pipe does is allow for a flexible portion of the pipe between the engine and the rest of the exhaust. GM had a service bulletin for a similar concern on some of the trucks. I will again post that bulletin at the end of the post. If your exhaust does not have a flex joint, I would recommend having one installed. This is something a local exhaust shop would be able to do for you. And lastly we can add mass (wieght) to your exhaust to try and help change the natural resonance frequency. This is also outlined in the bulletin I will provide for you. Keep oin mind that these are not what would be considered a gauranteed fix, however your going to have to try something to eliminate the posibilities. These are a few things that came to mind today. Having the dealer that is willing to work on it for you call GM Technical Assistance is highly recommended. As you can imagine they get a much larger database of concerns and fixes. They also have access to unpublished service bulletins. You may not be the only person to experience this, and they may have a solution for it. I am not able to call without having the vehicle in front of me. As promised here is the bulletin I was refering to. This bulletin does not specifically apply to your vehicle, but it is a similar concern. The bulletin number is XXXXX

Subject:Exhaust Moan/Vibration Noise (Install Exhaust System Flex Pipe Kit And Exhaust Dampeners, If Necessary)
Models:1999-2007 Chevrolet Silverado 1500 Series Extended Cab or Regular Cab/Long or Short Box Pickups (Classic)
2007-2008 Chevrolet Silverado 1500 Series Extended Cab or Regular Cab/Long or Short/Standard Box Pickups (New Body Style)
1999-2007 GMC Sierra 1500 Series Extended Cab or Regular Cab/Long or Short Box Pickups (Classic)
2007-2008 GMC Sierra 1500 Series Extended Cab or Regular Cab/Long or Short/Standard Box Pickups (New Body Style)
with 4.3L Engine (VINs W, X -- RPOs L35, LU3) and Automatic Transmission (RPO M30)

This bulletin is being revised to add the 2007 and 2008 (New Body Style) model years, update the warranty information and add information for installing exhaust dampeners. Please discard Corporate Bulletin Number 02-06-05-003F (Section 06 -- Engine/Propulsion System).


Some customers may comment on a moan or vibration noise at low vehicle speeds 40-64 km (25-40 mph) or between(NNN) NNN-NNNNRPM under load.


Exhaust system resonance may be transmitted through the powertrain mounts into the body causing this condition.


Caution: Personal injury or burns may occur when working on a hot exhaust system, let the exhaust system cool off prior to performing the repair.

An exhaust system flex pipe kit is available to correct this condition. If diagnosis leads to this condition, install the applicable exhaust system flex pipe kit listed below using the following procedure. Refer to the Parts Information for kit applications and usage.

Important: This fix and the kit part numbers are specific to vehicle frame type. A Level 3 frame was introduced interim 2000 model year (approximately January 2000). With a Level 3 frame, the transmission crossmember was moved forward of its previous location. Pre-Level 3 frames will require the installation of additional components to correct the condition.

1999-2000 4WD Models Built Prior to 1/20/00 and All 2000-2008 2WD and 4WD Models Built After 1/00

These models require the installation of a flex coupling. The flex coupling has adapter sleeves for the installation of U-bolt clamps. This procedure uses the U-bolt clamps, but the preferred installation method is to weld the flex coupler to the exhaust pipe.

  1. Raise the vehicle.
  2. Locate the first available straight section of pipe rearward of the mid-joint flange and forward of the muffler assembly.
  3. Measure approximately 228 mm (9 in) on the straight pipe and mark.
  4. Using a suitable cutting tool, cut out the marked section of the pipe and remove.
  5. Remove any burrs, if necessary, before installing the flex coupler pipe.

  6. Object Number: 892150  Size: SH

  7. Install the flex coupling (1). Expand the sleeves of the flex coupler, if necessary, to properly fit over each pipe end. The centerline of the installed flex coupling should run parallel to the straight section of pipe (no bends in the coupling) for optimum performance.
  8. Install the U-bolt clamps (2) on each sleeve end of the flex coupling.
  9. Tighten
    Tighten the U-bolt clamps to 30 N·m (22 lb ft).

  10. Lower the vehicle.
  11. Verify that the condition has been fixed.
  12. If the exhaust vibration or moan is still present, order two exhaust dampeners, P/N 10199232, and proceed to Installation of Exhaust Dampeners, If Necessary in this bulletin.

Installation of Exhaust Dampeners, If Necessary

  1. Locate the bend in the exhaust pipe over the rear axle.
  2. Measure 102 mm (4 in) back on the straight portion of the exhaust pipe and mark the location.
  3. Tip
    The two dampeners should be installed close to each other on the exhaust pipe, but the dampeners should not touch together.

  4. Install the two dampeners, P/N 10199232, starting at the mark on the exhaust pipe with the weights pointing up towards the underside of the pickup box.

1999-2000 2WD Models Built Prior to 1/00

These models will require the installation of a flex coupler, two Y-pipe support brace rods w/integral U-bolt clamp assemblies on the LH and RH sides of the transmission rear mount and new transmission mount studs and nuts. The Y-pipe support braces are used in combination with the flex coupler to reduce exhaust moan.

  1. Install the flex coupler using steps 1-7 in the first procedure.
  2. Support the transmission with a suitable adjustable jack stand.
  3. Remove the two bolts and nuts from the transmission rear mount.
  4. Position the transmission rear mount and install two new studs to the mount.
  5. Install the new studs supplied with the kit to the transmission mount.

  6. Object Number: 892151  Size: SH

  7. Loosely position the Y-pipe support braces w/integral U-bolt clamps (LH and RH) to the underside of the transmission rear mount and the crossover pipe as shown. The top ends of the braces attach to the underside of the transmission rear mount. The bottom ends of the braces attach to the crossover pipe using the integral U-bolt clamps. The braces support the LH leg of the Y-pipe where it crosses over the vehicle to meet the Y-pipe collector.
  8. Install the two nuts to the transmission rear mount and the two nuts to the U-bolt clamps.
  9. Tighten

    Tighten the new transmission mount nuts to 25 N·m (18 lb ft).
    Tighten the two U-bolt clamps to 30 N·m (22 lb ft).
  10. Lower the vehicle.
  11. Verify that the condition has been fixed.
  12. If the exhaust vibration or moan is still present, order two exhaust dampeners, P/N 10199232, and proceed to Installation of Exhaust Dampeners, If Necessary in this bulletin.

Parts Information

Part Number




Exhaust System Parts Package

1999-2000 2WD Models Built Prior to 1/00


Exhaust System Parts Package

1999-2000 4WD Models Built Prior to 1/20/00
All 2000-2008 2WD and 4WD Models Built After 1/00


Exhaust Muffler Vibration Dampener Assembly

2-If Necessary

Kit P/N 15076982 includes a flex coupler, two support brace rods w/integral U-bolt pipe clamps, two U-bolt pipe clamps (for use with flex coupler) and two new transmission mount studs w/fasteners.
Kit P/N 15076990 includes a flex coupler and two U-bolt pipe clamps.

Customer: replied 7 years ago.

Cannot tell you how we cannot wait to come home from work (late as we do) to get your email.

Regarding your thorough investigation (very impressed), please explain:

1. Thought the other bulletin indicated AFM would only be a problem at 4 cylinders and yet I have no noise/vibration at 4 cylinders -- only 8 cylinders. What RPMs on this AFM is supposed to leave 8 and drop to 4?

2. I did visit both a national corporate transmission as well as a muffler place in my neighborhood today and they were very nice and drove the car with me and indicated exhaust also! They noticed the noise/vibration right away and said they had had others complaining about the same with the same engine I have. They just will not touch a warranty car. And they said mine was much more severe than should be considered normal.

The transmission and muffler guys told me this noise/vibration is too excessive and definitely not normal. They told me about a man's wife who complains of headaches from her long ride in her Surburban to east Long Island (same engine, etc). He had her vehicle's exhaust pipe switched from 3 to 2 inch and it made the matter worse so they switched it back.

The transmission guy and muffler guy both gave me the word 'resonance' which you already had! Very impressed again.

BUT now...regarding your 'cures' (I know there may be no permanent fix but yes I want to enjoy my ride and at least suppress the excessive noise and vibrations into the cabin which overpowers my radio)--

1. Rubber mounting -- I will ask the 'friendly' dealership if they are willing to check this even though there is a 'feeling' of 'you did buy your vehicle here' and if they refuse, who should I go see?

2. My exhaust does have a flex joint -- no need to install -- but maybe it needs to be aligned or replaced? Maybe it is malfunctioning or has a hole?

3. Mass weight - I again will definitely ask the 'friendly' dealership -- perhaps if I promise to have all my oil changes there, they will feel as if there is some business and not just warranty work.

4. I will ask them if they can call the GM Technical specialist. Am I able to do that if they won't?

Actually, the original dealership should be doing all this that I took a loan for $58,000 and they dropped me and my car. I plan on contacting the owner to see if the owner is aware of the lack of service I have received.

Whatever, I will definitely give you feedback.

By the way, just so you know -- you earned your pay with bonus. I just don't want to lose you yet if you don't mind!

Talk to you soon.
Sorry about the dealy today. I was attending a High School Football Playoff game. I will gladly answer your questions, but it will be around lunch hour on Saturday. Thank You for your patience.

That has to be a bit of relief knowing that it has been isolated to the exhaust system, knowing it's not something safety related. As for AFM operation, there is a whole list of enable and disable criteria for AFM operation. Everything from engine temp, RPM, transmission gear, throttle position, engine load, etc......, all factor into AFM operation. There really is no set time or RPM range this happens in. When engine load is high it will be in V8 mode, and when load is low (like at cruise) V4 mode. I am also a little sketchy on the display. I think AFM is more active than the display indicates. AFM operation is virtually seamless, meaning it's hard to detect the change to and from V4 mode. As far as your rubber mounting question, if the dealer will not check the exhaust for you then any shop should be able to do this for you. Obviously you will have to pay for the services you recieve, but I am sure your aware of this. You are just trying to make sure the exhaust system is not touching the frame or body anywhere and that the rubber mounts are in good shape and positioned to allow for movement to isolate vibration. If your exhaust already has a flex joint there is no need to replace it. I am sure it's functioning as designed. If the joint is factory there is no alignment that can be done to this joint, as it is likely welded into the exhaust. Adding mass to the exhaust system is a trial and error process, moving and repositioning the weight untill the exhaust is tuned to help reduce the resonance. If your dealer is not willing to do this you may try the exhaust shop. The bulletin has the part numbers listed for the weight, and you (or the exhaust shop) can order these from any dealer parts department. Unfortunately GM Techniacl Assistance is only avliable to dealer employees. In order to cal you have to have the vehicle, an open repair order, and a few other things. The phone number I gave you for GMC customer service is where you could call. They will not have technical data and are more geared to assist you the owner, but none the less it's avliable to you. This thread will continue to remain open as long we continue to post to it, it will not close because you accept the answer. Thank you for your compliments and thank you for using Just Answer.


Customer: replied 7 years ago.

Glad you were out but we did miss you.
Did they win the game?

Thank you for all your responses, and although we are hearing overall from the tranmission and muffler experts and now today from a body/repair shop owner and gas station mechanic -- they are all telling us that this noise/vibration is real and apparently a problem with the AFM and GM cars.

Is that true?
That GM has a lot of complaints from owners?
Is there no fix by GM?

The mechanic said he just got the Escalade with 6.2 liter and no AFM and is having no problems and that he knows many customers with the same problem I am having with my 5.3 liter with AFM -- and that it will only get worse as mileage and time goes.

Do you know that to be true? Are there any other bulletins I need?

One guy told me that one owner had his 6-month Surburban 3 inch pipe altered to a 2 inch pipe and that just made the situation worse so they went back to the 3 inch pipe and then sold the car. How terrible and they did not buy another GM.

I have been a GM car owner for years -- this one is really puzzling me.

Can I ask -- why would the car feel as if it is going uphill when I got the noise/vibration and yet I am on 1500 rpms on a steady 60 miles per hour on straight flat highway? Is that the AFM or the exhaust or a combination? Feels and sounds like a diesel truck going uphill!? The sound echoes into the cabin -- like groaning.

I will try to take the vehicle back to the original dealer this week with the bulletins you provided -- as doing something is better than doing nothing - to try to reduce/eliminate the noise/vibration. AND I will insist they call the GM tech from the dealership.

Should he be asking for anyone in particular? OR anything in particular?

I just don't know if they will do anything. If they don't, or say they did and nothing works -- then what?

P.S. Do you know if the 2010 will be different and not have this problem?
I am not aware of any problems in mass as far as AFM goes. I can honestly say that as many of these vehicles that we see, there seem to be a very minor amount of problems related to AFM. AFM has been avliable in GM vehicles since 2006 or 2007 I think. That being said I don't think that there is really any problems with AFM as a concept or in practice. I am only speculating here, but I think it's a combination of the 6spd trans and AFM working together that may cause some of this noise/vibration. The only problems I have seen are with the 2010 Camaro, which is also equipped with a 6spd auto trans. the noise on these vehicles is slightly more than normal. I am not trying to downplay your noise as I have not heard it, and also know that each vehicle is somewhat different. A Camaro is not a Yukon and vice versa. Next time you get the noise to happen try acellerating gradually. The goal here is to create enough engine load to disengage AFM if it were active, but not to make the trans downshift. If the noise goes away at some specific point, then it's AFM and it's effect on the exhaust that are creating the undesireable resonance. Technical assistance is a call center that is staffed with technicians and engineers that are familiar with GM vehicles. They are a good resource when used properly. I hate to say it, as I would not wish to loose a GM customer, but GM does have the 60 day moeny back garauntee that you see and hear advertised. If you fall within this time frame and mileage you might get some help from that policy. I can not speculate on the 2010 models and if this problem will also be present. If I were you and was considering a 2010 model to solve this concern, I think I would opt for a non-AFM model. From my experience AFM is a minimal improvement to fuel economy for most drivers. One other thing you could try; does your Yukon have the manual shift mode? The gear position indicator usually displays "M" and there are + and - buttons on the selector lever. If you do have this option you could try to downshift the trans manually into the first gear lower to see if the noise also goes away. This will effectively raise the engine RPM sligtly and the noise may disapate. This is obviously not a long term solution to this problem, but maybe one more thing you can show the dealer. We did win the game by the way. 2 more games to the state finals, go little hawks! Thanks for asking.
Customer: replied 7 years ago.

I am willing to try anything to resolve the noise/vibration which is possibly coming from the AFM with the 5.3 engine combination OR the exhaust -- at least that is what I am being told from so many sources -- except the GM dealership continues to say it is normal.

The transmission guy said the transmission was good and blamed the exhaust.

Question #1: why when I drive at 45- 60 miles per hour on straight road, does the car make that growling diesel truck sound as if it is going uphill and that stays with you esp at 1500 rpms?

As a mechanic, what would be the greater factor -- AFM or exhaust?

Regarding the 60-day money back guarantee -- bad sales pitch from that salesman from the dealership as he advised not to take it because you would never get the title in time to even apply for it and return the vehicle. I never ever bought a car - but leased all my Surburans for 30 years. Engine was never ever problem from the 350 to the 5.3 engines.

Question #2: If it does get that far, am I still eligible?

Question #3: If the dealership does not accomodate me with the GM bulletins you provided for service -- do I need GM approval to go to another dealership according to the warranty you forwarded me?
In my professional opinion I would say it is neither the fault of one system or another. It is in fact a combination of the 6spd trans (the gearing determines engine cruise RPM), the AFM (changing from 8 to 4 cylinders and back), and then lastly the exhaust system (its natural resonance) that are combining to create the noise/vibration. So altering one of those factors could cure the problem. The easiest and most economical of which is the exhaust system. Adding the weights to help change the resonance is the method I would try to change the exhaust. Chnaging the exhaust entirely is not likely to achieve the desired result in my opinion. As far as the 60 day warranty, I am not familiar with the sales end of the business. If I were in your situation I would contact GMC customer service to answer those questions. I am not sure of your eligibility, again GMC customer service would be who I would call. You absolutely do not need GM's approval to go to another dealer. Cross line warranty was desigined to help reduce negative ownership experiences. It is however voluntary and not required by a non GMC dealer. If you find another GMC dealer they have no choice but to address your concerns.
Customer: replied 7 years ago.

You are very good and your responses are appreciated. This will be coming to an end for you -- have we held on to you the longest?

I will be contacting the dealership and/or dealership owner this week for an appointment and they should be reviewing the GM bulletins you provided. They were just patronizing because they kept calling it normal. They did call me Friday and promised to get back to me and did not on Friday. I will try this week.

If they do not accommodate, I will contact the other GM dealership (thanks for that info on cross warranty). They at least heard the noise and admitted something needs to be done although they did not think GM had a real fix. Your bulletins are definitely worth a try.

Hopefully steps 1 or 2 will find a resolution to reduce the noise/vibration to just a tone which I understand is considered normal. The going up a hill on flat road growling vibrating moaning diesel/sports sound most of us all agreed (except for my dealership) is not normal.

Thank you again. You have kept a good name for GM and a good method of communication which is much appreciated for dialogue and review.

Talk to you real soon as I am sure you would like to know the final outcome.

Hope your team continues to win.

P.S. How do we get your pay and additional bonus to you -- make sure no one else gets it but you?
Thank you for your patronage. I take pride in my work and the product I represent. All you will need to do for your deposit to be applied is press the ACCEPT button which I believe is in the upper right corner, (My interface is not exactly the same as yours). I believe the bonus can be applied there as well. I am very intrested in the outcome. I hope for your sake that there is a easy resolution once you finally get someone to work on it for you. You can just continue the dialouge here as far as the solution goes. Thank You for using Just Answer.

Was reviewng all avliable service bulletins for the 2009 Yukon and ran accross a few that indicate some noise being heard when the vehicle is in 4wd or Auto modes. I think we already covered this but just make sure you are driving in 2Hi mode unless road conditions require 4wd. There have been cases of vehicles in 4Hi causing a noise/vibration. Just thought I would pass that along to you as well. And I don't think your vehicle is a 3/4 ton or 2500, but a very similar concern noted here in this bulletin:


#PIT4953: Rattle Or Buzz Type Noise From Underbody Of Vehicle At Light Throttle - (Nov 4, 2009)

Subject:Rattle Or Buzz Type Noise from Underbody Of Vehicle At Light Throttle

Models:2009 Chevrolet Suburban
2009 GMC Yukon XL
2500 Series Models Only.


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


Some customers may comment on a rattle or buzz type noise coming from the underbody, exhaust, or engine compartment on light tip-in throttle at approximately 30-40 MPH. The condition is most often seen when the vehicle is warm and has been running for 5 minutes or more.

The concern may be caused by a loose connector joint for the center baffle tube inside of the exhaust muffler. To isolate the concern, warm vehicle up by driving approximately 5 miles. Pull up parallel to a wall and roll down side windows. While in drive, apply the brake and raise engine speed to 1600-1800 RPM. The rattle or buzz type noise should be present in the exhaust muffler if this condition exists and can be isolated with chassis ears or a stethoscope.


If the noise is isolated to the exhaust muffler, the muffler pipe assembly will need to be replaced.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Customer: replied 7 years ago.
Guess what!

Got a phone call suddenly today from the dealership salesrep I bought the car from and he told me that the dealership is having a General Motors engineer coming in within 48 hours to handle this car.

They are giving me a loaner and told me to be ready for a phone call.

1. Do I tell him about all the testing I already performed?

2. Do I give him all these bulletins to look over?

3. Would this be the GM technical specialist you referred to?

4. What will he be coming to do? -- at a dealership without any advanced computer technology.

5. WHAT should I expect and/or do?

I respect your professional opinion and honesty on this matter.
Customer: replied 7 years ago.
Will await your input
Customer: replied 7 years ago.
OK -- just checking in to make sure I did not lose this post. Late last night when I realized I forgot to shut down the PC, I thought I lost you.

Talk to you tonite.
If this engineer is really from GM (given your past experiences I don't put a lot of faith in the sales rep) then he/she is likely a field service engineer. GM's field service engineers work closely with brand quality and other engineers within GM. The most important thing for you to do is to give an accurate description of your concern and even possibly even demonstrate the concern to the engineer if necessary. A field engineer will have access to all of the service bulletins that we have reviewed as well as any internal unpublished bulletins that I do not have access to. He/she will also have the necessary equipment for testing and possibly some repairs. The engineers main focus is to report the cause of this concern back to GM, to help develop and implement a repair for vehicles that may be exhibiting the same concern. Your concern may be corrected by something as simple as a different engine or transmission calibration. He/she may have such a calibration with them, they may not. You should expect nothing more than they are investigating your concern and will then use that data and observations to first classify the noise as normal or not, then possibly develop and possibly implement a repair. All in all this is a positive thing if GM is sending a field engineer. You may have to be patient and do your best to work with the engineer and service staff to get your concern resolved. The good news is that somebody is now paying attention to your concern. I have a good feeling that GM is watching over a lot of these blogs and public forums in an attempt to keep a positive public image. At any rate congratulations, now hopefully you get the result you desire. Keep me in the loop, as this is interesting to me as well.
Customer: replied 7 years ago.
Glad we didn't lose you!

I don't think I ever told you we comleted the Purchase and Delivery Satisfaction Survey emailed to us just last week. We rated a satisfactory purchase but very unsatisfactory post-purchase.

So guess what -- another surprise -- TODAY I got a call at my business from a GM customer service rep who claims she is next in line to Scott Lawson, Director of Customer and Relationship Services.

She said our unsatisfied Survey due to the fact the dealership would not even look at GM bulletins or put the car on a lift to try to review and resolve the problem -- prompted for GM to request a 48-hour field Engineer at the dealership. That is why the dealership called me.

So we do know that it is really a GM engineer.

She inquired about others driving the car and I informed her that I took my car to another GMC dealership as well as a local mechanic as well as a brand name muffler and also a brand name transmission place and all their mechanics indicated the noise is not normal -- too excessive -- and possibly the exhaust. Or as you indicated, could be a combination of AFM with exhaust or even possibly transmission. Whatever, it is annoying.

Are you ready for this? I finally came to the conclusion after 2 long rides for business in my vehicle today that the sound in the engine at 1200 -1600 rpms is most like a 'auger in a washing machine" with a full load of wash. I really had a headache today and took motrin at a local pharmacy.

Talking on the phone, the GM rep said she wants the field engineer to look over the car from head to toe. She gave me her name and number and wants the field engineer to notify her as soon as he gets there.

She told me to just tell him what I have experienced with the feel and sound of the car while driving. She also noticed that I have had 22 GM vehicles in the last 40 years of my driving life with 9 Surburbans in the past 12 years.

Any other advice or just ask the Engineer what he wants to know from me? I want to just tell him to drive it at least 10-15 minutes on steady driving to get the car hot and then drive at 1200-1500 rpms gradually accelerating from 45 to 60 mph and then remain at a steady pace for 10 minutes. NOTE: The vehicle remained at 8 cylinder and never dropped to 4 as should be expected. The sound is worse when you need to accelerate to an incline but also remains at straight driving as if it is on an incline. There is no normal engine sound but loud vibrating noise which overpowers the radio.

The sound only disappears when coasting with your foot off the gas pedal.

I will definitely keep you informed as you have given me an avenue to explain and dialogue to help me get through this.

Just hope for the best now!

P.S. That salesrep who called me the other day asked if I were getting nonsense off the Internet. I said I was in contact with GM experts attempting to assist me.
I would just give the engineer any info they request just as you have to me as I have asked many questions. They will do thier best to remedy this for you. As you can see they do value your opinion and it has spurred call to action for them. That's great news and I am sure you are headed down the road to a fix. Let me know how it all goes. Thank You.
Customer: replied 7 years ago.

We will definitely keep you in the loop!

Hoping for the best.

Thanks again for everything as you are an expert in your own right.

Talk to you again very soon.
No problem for the info. Good luck. I think you are in good hands now.
Customer: replied 7 years ago.
Surprise - Surprise - Surprise.

Today I got phone messages left at my business, my home and my cell phone so I thought the dealership had the Field Engineer there. Then when I got back to my business it was the service advisor who always gave me a hard time on the phone (who had refused to put the car on the lift or take the bulletins or even drive long enough to really hear the noise) -- and he said he was to inform me that there is a bulletin for a damper for the exhaust and to schedule my car next week.

I was shocked and asked when was the Field Engineer coming in as the salesrep as well as GMC Customer Service assistant indicated to me just 2 days ago within 48 hours from the Northeast area. This advisor laughed and told me no engineer was ever coming and that the salesrep was misunderstood by me and worse that the GMC rep lied to me and that he just spoke to her.

I tried reaching the GMC rep but she was gone for the day so I intend to call her tomorrow to find out what changed.

The service advisor at the dealership said they had a bulletin which they cold not release to me as it is privilege and he already notified me again today that the noise is normal and that once the damper is put on, he has no intentions of driving the car for over 10 minutes as he does not get paid to do that!

WHAT bulletin?
What is a damper?

What should I do?

I am really upset and called this all crap and want to talk to the Customer Service rep tomorrow because she told me an Engineer was coming but that I had to still use this dealership for one more chance.

What do you think?
What do you advise?

I could really use some help.
Customer: replied 7 years ago.
Do you think it is the damper bulletin you gave me already?

Sorry I missed you last night, it was a late night for me. Again I am shocked by the lack of this dealer to want to fix this for you. Appalled does not even begin to describe it. As far as the bulletin goes I can only speculate on what it may be. It's a good bet though that they may have been instructed to do this by GM. The damper they are refering to I beleive is the weight/damper that we spoke of earlier and that you have the bulletin about. If by chance this is an internal unpublished bulletin from GM Technical assistance, then there is no copy to print and see. Usually when I have encountered an unpulished bulletin they only give you a bulletin number to refrence, then instruct you as to the repair. However GM service bulletins are not "privileged", there is a federal law that in a nut shell requires this information to be released to he public. This way the independent repair facilities have adequite information for diagnosis and repair. Your contact with GM Customer Service is really who I would be concentrating your effort to. If it were me I would also tell the Customer Service rep that you once agin have been treated the way you have and that you no longer trust them to perform ANY work on your vehicle. Ask where an altrenate site could be. Dealers like that deserve to feel the rath of any hammer that will fall on them. I am sorry I usually don't engage in down talking anyone, but dealers like that give the rest of us good ones a bad name. Let me know what you find out from Customer Service.

Customer: replied 7 years ago.
I appreciate your comments and you only seem to know how mad I am here.

But good news is that the customer service rep answered my call today and let me know that she told the service advisor to contact me and had no idea how demeaning he would be.

She said on his behalf that he is annoyed that I sought out other assistance (other mechanics, transmission, muffler and the other GMC dealer) who all agreed there is a real problem. That service advisor told her that he believes (without any proof) that I must be googling on the internet and getting a lot of misinformaiton. But I reminded her that he was the one who refused to look up any bulletins - even look over the ones in my hand -- and even refused to put the car on the lift. I also let her know that the business cards I have are of real people who drove my car and that you can't drive the car on the internet. (Do you think they are afraid of experts with knowledge like you on the internet?)

She told me we have to give the dealership one more try but promised it would be a last chance. She also assured me that the Field Engineer offered the bulletin to remove/reduce the incoming noise into the cabin (sounds familiar!) and that General Motors is sending the part to the dealership.

I do believe it is the bulletin you already gave me.

The GMC rep then told me to let the dealership work on based on the bulletin that the Engineer is giving them and that the dealership will keep the car for 2 days. She also said she will call the dealership and tell the service advisor that the service mechanic working on the car must take the car home and bring it back the next day as a test run -- since he refused to take it on a 10 minute run!

Why do you think the dealership is so afraid of the internet with solid communications? Obviously, others must be using it too if they are so concerned.

Maybe they should just do their job and customers wouldn't have to find these sites. But thank goodness this site exists and you are out there -- otherwise, all I get from them is 'this is normal'.

You are my smoking gun with this dealership and I never had ever mentioned you or this site.

I have driven too many GM cars to ever think they know what they are talking about.

Here is one for you GMKindl --
Today I had 2 long runs with the car hot and on the Parkway, I put the car into 62 mph CRUISE CONTROL for 12 1/2 minutes. The car NEVER dropped into V4 mode! NEVER! And besides the seat, the steering wheel has a vibration sense now AND I am now hearing a new sound -- whistling? along with the washing machine noise.

Does this mean maybe the AFM is not working? Maybe my problem is not the normal tone of AFM but that the noise is due to a malfunctioning one?

Interested what your thoughts are as you seem to pinpoint everything with pretty good data.

Wish I could get you here!
Occasionally we do get customers who read chat blogs, and other model specific owner sites. Then on occasion, with an owner that is a car hypochondriac, that translates into my car does each and every one of these things listed in this bulletin. What that equates to is that a dealer tech has to verify each concern before they can fix the concern, or at least they are supposed to. This type of behavior is easily stopped by telling the customer they will be charged for diagnosis of their vehicle if the technician can not verify their concerns. Making them open their wallet usually deters this right away. That is the only legitimate concern a dealer may have about Internet sources. What they are forgetting is that there are credible sources available and that other owners could also be experiencing a similar concern. To think that just because they have never seen or heard of a particular concern that it does not exist is just plain ignorance. I have been doing this long enough to know that I have not nor will I ever see it all. I am not sure of what they are afraid of about Internet sources. I use the Internet daily in my work, I also use Gm sponsored and non-GM chat forums to help solve problems daily. These forums allow for experts across the country to pool resources and experiences to help find solutions to customer concerns. As far as AFM operation goes, like I mentioned before I think the display does not accurately show you AFM operation. I believe AFM is more active in newer models than the display may indicate. The other possibility is that AFM enable criteria are very long, specific temp, engine load, vehicle speed, engine run time, and a whole host of other engine specific sensor readings, it's just possible that the enable criteria were never all met. If AFM were not working, you likely wouldn't notice any noise as a result. Remember that the non-AFM vehicles didn't seem to have the noise/vibration? The normal noise in AFM engines is a result of the exhaust tone when AFM switches from 8 to 4 cylinders and vice versa. As far as the other concerns go.... make sure to mention them to the dealer. My gut instinct is that they may not be related, but I have been wrong before. All the details you can provide to the dealer will be helpful. If they choose to ignore them that's another story. I would focus on getting the original concern corrected before indulging another, as the solution for the first concern could correct other symptoms as well. I wish I was able to fix it for you, but just as it's hard to drive one on the Internet, the repair is just the same.
Customer: replied 7 years ago.
GREAT to know.

We will definitely keep you updated!
Will be looking forward to the cure.
Customer: replied 7 years ago.

Just an update -- maybe you know -- can't figure this out.


By accident today I performed a test on the car.

I was driving and accidentally put the car into TOW mode.


Guess what.


The noise/vibration stopped -- I simply had engine noise -- plus at 60 mph, straight run, within 2 minutes, the car went into V4 mode.


Can you explain this?


Remember, the car doesn't seem to get inot V4 mode on light load.


Just curious what you think.


Not really sure I can put a finger on what was happening for you. I do know that putting the vehicle in tow/haul mode does change things like trans shift points and I am sure a host of other things. Does the noise/vibration seem to be getting any better as you get a few miles on it? Is it changing at all? Have you had any luck with the dealer?
Customer: replied 7 years ago.

Glad to talk to you.


Yes -- the noise/vibration is is louder as I put on miles!


You said some time ago -- it could be a combination of the Trans, AFM and Exhaust some time ago. I guess you could be proven right!


On a light load driving for 12.5 miles, the car never went into V4 mode. All I get is the vibration and loud washing maching noise. It overpowers the engine. Like a diesel.


At what point at cruise control should my car have switched to V4 mode?


Tomorrow the car goes into the dealer for the damper. BUT, the GM customer service rep surprised me yesterday with a call for a follow-up which I thought was good and when I told her about this, she documented it and said she would tell the dealer.


So I guess I'll know something by the end of the week to inform you.


Are we your most interesting case?

AFM has quite a few enable criteria, so it's hard to tell definitvely when it will activate. I have provided a rough illustratition below for your refrence. I also provided the disable crieria, so if AFM is active and any of the disable criteria are met the system will go back to 8 cyl mode.


Object Number:(NNN) NNN-NNNN Size: MF

Cylinder deactivation may be inhibited for many reasons including the following:

Engine coolant temperature out of range for cylinder activation
Engine vacuum out of range
Brake booster vacuum out of range
Transmission gear incorrect or shift in progress
Accelerator pedal out of range or rate of pedal application to fast
Engine oil pressure and temperature out of range
Engine speed of range
Vehicle speed out of range
Minimum time in V8 mode not met
Maximum V4 mode time exceeded
Decel fuel cutoff active
Reduced engine power active
Torque management active
Catalytic converter over temperature protection active
Piston protection active, knock detected
Cylinder deactivation solenoid driver circuit faults

I have seen many intresting things throughout my career. This does rank roght up there though. Keep me in the loop.


Customer: replied 7 years ago.

Took the car into the dealership today.

The service advisor Mike was surprised to see me and asked me why was I there.


I reminded him that the GM rep Jennie informed me to come in as the damper was at the dealership with the clamp.


He knew nothing about it. He called the part dept and they informed him they were ready for me.


I had to wait 45 minutes before they could bring the car around to test drive!


I explained I was here for the possible AFM problem. The service advisor Mike asked what that even was???!!!??? No joke.


He then insisted no paperwork was needed but I insisted paperwork was required as per the GM rep to have a service report completed. I questioned his wording on the report but nothing changed.


He then called the owner Coleen and said 'this guy has papers hear about an AFM problem and I don't know anything about this.' I gave him some copies of literature on the subject matter on the patent and functionality of AFM.


This service advisor and 2 techs then took the car on a ride with me in the back seat as advised by the GM rep. One of the service techs Jeff was driving the car and the other service tech Dave was in the back seat with me. After 10 minutes, the 2 service techs (one driving and one in the back seat with me) admitted they heard a "groan" and/or a "moan" and felt a "vibration" -- 'like going uphill'. The one tech even put his hand on the backseat floor.


The service advisor Mike still heard nothing and gave looks to the others and seemed most agitated with them.


As we were driving, I asked why the car never goes into V4 at 60 mph at 10 minutes cruising at a light load with no wind resistance. The tech driving responded that the car only goes into V4 mode when you coast off the gas!!!


The service manager (who knew nothing about AFM before) now agreed.


As the service tech was driving, he announced to everyone in the car that the car was at V4 mode at this time. I pointed out to him that his foot was off the gas pedal! When I told him to drive at 60 mph and lock the car into cruise control and watch the DIC and the rpms -- the car NEVER went into V4 mode and the 'groaning' was very evident. The service techs said nothing and the service advisor said it was normal.


I reminded him that a 'tone' is nothing similar to the 'excessive groaning' this car is experiencing. My other Surburbans went into V4 mode at 60 mph in cruise control giving me 21 miles per gallon energy efficiency. This car cannot.


Why would this car not go into V4 mode to save fuel? That is what it was patented for.


Now when we came back to the dealership, the service manager mentioned that the damper would go on the car. The tech Dave said that the damper and weights should eliminate some of the noise. The tech Jeff (driver) simply walked away.


The service manager once again said he still heard nothing so I responded 'remember -- 2 techs heard against 1 (you saying normal).'


I got a loan car - same engine and same transmission -- and guess what -- comfortable enjoyable ride -- no noise, no struggling of uphill, no vibration. The car went into V4 mode as expected as I drove during the day on my usual runs.


In the afternoon I got a call from the service advisor Mike who heard nothing and he said - they put the damper on and there was no change.


Now the advisor informed me that they would be contacting the Field Engineer who recommended the damper and request he show up asap.


I tried contacting the GM rep Jennie and she was not available at 5 pm when the dealership called me.


The saga continues...

It is indeed a saga at this point. It appers anyway that somebody is now at least trying to address the problem. They must also think there is some validity to the concern if they are keeping the vehicle and contacting the Field Engineer. I think you finally have the attention of some of the people at GM. Keep your contact at GM informed and up to date. I truely am sorry for the difficulty your dealer continues to give you, appologies don't fix your concern but hopefully you know not all dealers and techs treat thier customers like you have been treated. I will be awaiting your results. Good luck!
Customer: replied 7 years ago.

I slept on all this last night and decided to call the GM customer rep first thing in the AM..


She responded with apologies for how I was treated and escalated the issue to her supervisor who got on the phone with me.


They assured me they would be calling the Field Engineer and I told them I did not want that service advisor anywhere near my car again.


For anybody to tell me that the AMF works when coasting -- even she knew that stepping on the gas causes the V4. Every car I have ever had never had this problem.


The service manager has called my office and left message to call him back but I called the GM customer service and they told me to avoid any phone calls for 24 hours until I heard from customer service.


The supervisor was calling the dealership owner.


I liked what the customer service rep said to me -- even it is were normal, the dealership was supposed to use resources available to satisfy the customer. She even said I should not be concerned about his remarks of normal as she could understand why I did not want him near my car when he did not even know what AFM was or how it worked.


REALLY appreciate all the info you send.


Wish you were here fixing it and I am sure I would be driving my GM with enjoyment.


Will definitely keep you informed.


P.S. The loaner I have now feels and sounds just like all my other GM cars. I real joy to drive!



Customer: replied 7 years ago.

SO aggravating.


The service manager was leaving messages at work and home of simply "call me" for the past few days.


Then on Friday, 4 PM the GM new rep (escalated) informed me that the service manager called them and informed them that the Field Engineer was already there and tested the car and it was fine.


SO -- the GM new rep told me that would have to take the word of the Field Engineer and then also told me that the service manager said I had to pick up my car first thing Saturday AM or pay penalties with the loaner car.


I WAS FURIOUS. The other GM rep promised me that the service manager would never set foot in my car again as per my request -- and that I would be able to either speak with or at least test drive the car with the Field Engineer.


GM offered compassion but no resolution!


SO -- On Saturday early AM, I returned the loaner and went to the dealership.


The car pulled to the front for me -- but when we inquired about the paperwork -- THERE WAS NONE!


We refused to take the car without paperwork so the salesrep called the service manager on the phone but came back to tell me there was no paperwork.


We refused to take back the car without paperwork.


We then had to get a loaner again.


I intend to report this to GM with the following inquires:

1. Was there really a Field Engineer?

2. WHEN was he there testing my car?

3. WHAT testing did he perform?



I want paperwork to document what was done!


By the way, I read that there is a 'GM memo' or TSB regarding the noise/vibration issue. Is that what you gave me already?


Any other recommendations?


p.s. What is Diablosport Predator and Cortex ? Was told by others that it is the fix I need.


I want GM to make good on this car.

I am hoping the muffler and weights if put on my car would help.

BUT what if it doesn't?

Customer: replied 7 years ago.

SO aggravating.


The service manager was leaving messages at work and home of simply "call me" for the past few days.


Then on Friday, 4 PM the GM new rep (escalated) informed me that the service manager called them and informed them that the Field Engineer was already there and tested the car and it was fine.


SO -- the GM new rep told me that would have to take the word of the Field Engineer and then also told me that the service manager said I had to pick up my car first thing Saturday AM or pay penalties with the loaner car.


I WAS FURIOUS. The other GM rep promised me that the service manager would never set foot in my car again as per my request -- and that I would be able to either speak with or at least test drive the car with the Field Engineer.


GM offered compassion but no resolution!


SO -- On Saturday early AM, I returned the loaner and went to the dealership.


The car pulled to the front for me -- but when we inquired about the paperwork -- THERE WAS NONE!


We refused to take the car without paperwork so the salesrep called the service manager on the phone but came back to tell me there was no paperwork.


We refused to take back the car without paperwork.


We then had to get a loaner again.


I intend to report this to GM with the following inquires:

1. Was there really a Field Engineer?

2. WHEN was he there testing my car?

3. WHAT testing did he perform?



I want paperwork to document what was done!


By the way, I read that there is a 'GM memo' or TSB regarding the noise/vibration issue. Is that what you gave me already?


Any other recommendations?


p.s. What is Diablosport Predator and Cortex ? Was told by others that it is the fix I need.


I want GM to make good on this car.

I am hoping the muffler and weights if put on my car would help.

BUT what if it doesn't?

Customer: replied 7 years ago.



GM confirmed to pick up the car today as we complained to them that the car had no paperwork.


Ironically, the paperwork was now done but indicating how the service manager Mike F. was behind getting the escalation and the engineer.


Whatever. I made a complaint to GM that I requested a drive with the Field Engineer and instead that service manager drove with him.


The big news is that remember when I told you how Tow Mode make the car fell right? Well now with the damper and clamp -- the car is worse than ever even with the Tow Mode. I used to have peace at least in the Tow Mode and now I cannot tolerate.


GM said there is nothing more they can do since the Field Engineer found normal drive.




I will make a complaint to GM that the damper and clamp is worse. Maybe these dealership techs put in on wrong? I don't know.


Can it come off again?


I'll talk to GM tomorrow.

Ughh....I am sorry to hear you have had ill results with the field engineer. The dampner and clamp, if it's the same as I have installed previously, is easily removed. If it's what I think it is, it is held on by a simple u-bolt type exhaust clamp. Removal of the clamp will allow the damper to be removed. Like I said before moving the damper to different parts of the exhaust pipe assembly may yield different results. This is somewhat of a tuning procedure. There are obviously space limitations as to where the damper can be placed, but space is the only limitation. As far as your other question about Diablo sport and cortex, I am assuming these are after market programmers that alter the factory tuning of the engine. These will indeed alter things like AFM operation and a host of many other things. The real caution here is that if you install non-factory calibrations into the Engine Control Module (ECM) and there is a drive train failure that can some way be attributed to the calibrations it will void any warranty on the related component. With the cost of engines, transmissions, etc.., it is a gamble. If it were my vehicle I would steer clear of these options, but only my opinion. Make sure when ever you take your vehicle in for service at ANY service facility you get a copy of the invoice. In the case of the dealer this is the only way it can trigger a service satisfaction survey similar to the sales satisfaction survey you already returned. The only other advice I can offer is to be persistent, but not overbearing, sooner or later they will get tired of the issues and either trade you into a different vehicle or fix the problem. The whole squeaky wheel gets the grease theory.
Customer: replied 7 years ago.

We did talk with GM just today and they did indicate they were calling back as a courtesy for feedback.


The GM rep (escalated) who first told us we could never drive with the Field Engineer -- now listened to our complaint about the installation of the damper and clamp & informed us that the Field Engineer was coming back 1st week of December for a one-on-one test drive!


GM also honored our Cross Warranty request (thank you) and I as the main driver, I am meeting with the Field Engineer next Tuesday at 9 AM at another dealership (which they recommended and with whom I would prefer to go to!)


I am glad the damper can come off if needed -- or even moved if needed.


The problem is that this noise just never leaves the cabin and I now cannot drive in TOW MODE which at least gave me some relief that I could listen to engine noise.


This is wasting so much time but we are being persistent and my wife tells me to stay calm and not be overbearing as you also said.

I never hated AFM before, but with this car (as good as it looks) it is just not enjoyable to drive.


If the ECM does need calibration, can't GM do it, and if so how?


How can you tell that the ECM is out of calibration? How can the Field Engineer know for sure it is the AFM? I want to know what I should be saying to the Field Engineer?


By the way, is it true what one mechanic told me that Canada is shipped GM cars without AFM?


Well, you have kept me going with some hope and much information.


Next week, hopefully the Field Engineer will find there is a problem and know how to fix it.

Customer: replied 7 years ago.



I am not sure you received my last response on 11/14 -- good news regarding GM allowing me to test drive with the Field Engineer.


Just simply want to know if there is any advice when I meet with the Field Engineer this Tuesday!

This should all be hopefully resolved this Tuesday!


You have been a great help -- better than anticipated.

Just wanted to end with giving you good news.


Please read my previous reply and answer the best you can as you always have and let me know.




Hope you had a great Thanksgiving.

Waiting to hear your answer to my reply!

Customer: replied 7 years ago.

Did you get my response on 11/24?


FYI -- the Field Sales rep from GM called today and said he will be driving with me and the Field Engineer also.


We are on for tomorrow 9 AM sharp!


Hope this is good new.


Any feedback before I go???

Thank You for the holiday wishes. Hope all was well for you too. Sounds like you are on the right path with GM. The people you will be driving with are the people with the power to resolve your issue. Whether it be fixing your vehicle or getting you into another vehicle. You have all the info that I come across. Good luck and let me know how you fare.
Customer: replied 7 years ago.



Just wanted to update you with today's events.


I drove the car with the GM Field Engineer Dan and the GM Operations Manager.


They let me take the car for 32 miles on the open highways -- on my usual routes for my business -- and guess what!!! THEY HEARD IT! They both looked around as I drove and acknowledged they felt the car suffering as if 'going up a mountain' and said it was internal and that whatever was causing those sounds was 'out of acceptable category'.


The Engineer had the car hooked up to some computer and at one point, whatever he did, he asked if I heard anything now and I indicated no! But I noticed that the rpms on the car were up. When he turned off that button on the computer, he even said 'now you hear the noise again' and I agreed.


THIS WAS THE SAME GUY that the other dealership took for a ride and he heard nothing with them! Wonder how they drove it for those simple 6 miles they took the car according to the report.


Then I asked him to drive the car back -- and he agreed!


While he was driving with me, he was listening and trying to determine where the sounds were being generated from. His face looked puzzled but determined. At one point, I asked him if his foot was vibrating, and he said the floorboard definitely was.


When we came out of the car, he looked around the car, told me he 'heard the noise' and the operations manager agreed -- and promised 'I am going to go back and try to find out what it is'.


When we came back to the new dealership, the Engineer took another vehicle out and we drove and all admitted that despite a 2009 with 5.3 liter -- no noise! The Engineer investigated and found that this vehicle had no AFM!


The Operations Manager said they would 'go back to the drawing board and see what can be done' to make my car just like the other car. The Engineer also informed me that so much time and effort could be costly to GM if the car cannot be fixed -- and when I inquired about a replacement car, the Operations Mgr said that GM would make that decision down the road. They just told me to sit tight and they would investigate and then contact me as this is a 'puzzler'.


What do you think!


I did what you said -- I was not overbearing, polite but firm and persistent. I hope you don't mind but I used your line: "I know you don't build the car -- but it's in your best interest to fix the car!"


This dealership also was pleasant and cooperative and indicated I could bring the vehicle here for whatever GM recommended!


Turns out -- my brother (another die heart GM guy like me) buys all his trucks and services them from this dealership. They treated me really nice.


The 2 GM guys were really nice too!


So what about that computer? What did he do to get rid of the noise? Is it a calibration or did he override the AFM? As a mechanic, do you know if the Engineer can download from the car without AFM and calibrate into my car?

Anyway, so far I am glad I listened to you and not buy any devices or go to any outside sources. I am glad these 2 GM specialist heard the sounds and agreed it needed to be addressed.


GM customer service later called me and confirmed that the 2 GM reps admitted they 'heard the noise' and that the 'Engineer is going to investigate' as to what can be done to 'make the car more comfortable.'


Do you want to know the final outcome? or do you want me to let you go know! You have been such a big help. Wish you were here.


Let me know!

I am glad to hear they have finally taken the time to duplicate the concern. Now they can diagnose the source of the concern and hopefully find a solution for you. I suspect what the engineer had was a diagnostic scan tool that was plugged into the vehicle allowing him to see various data to help diagnose the source. What he likely did was disable the AFM or some other component with the scan tool while you were driving. All GM dealers have this type of tool, a technician who can interpret and use the tool is a completely separate issue. As far as different engine calibrations to disable AFM - I am not sure what GM can do. I suppose there is some legal issue to deal wit has well concerning emissions and what the vehicle was certified for when it was produced. If anybody has the capability of doing that your engineer does. I am also glad to hear the new dealer has a better attitude towards customers. I think I would advise sticking with them for all of your repairs and maintenance.


Keep me informed as to how everything turns out. Hopefully they find a solution for you soon.

Customer: replied 7 years ago.



Have a quick question.


Can you help me on this one?


IF the NOISE and Vibrations and now sluggish ride (new development) is NOT due to the AFM needing to be calibrated or whatever...


How can I be sure it is NOT the AFM?


Is there a switch or button or cut off to the device to rule it out? (and I don't mean the over the internet devices people buy as I agree with you on that).


I am getting to think it is more of a piston problem or hole in the muffler?

Another mechanic I asked today said it could be the cylinder and told me to ask 'your friend' (which is you).


The noise is getting louder and the ride is getting more and more sluggish.


Any feedback?

What did the engineer say? Did they make any repairs at all? There is no easy way to disable AFM without cuasing other problems that would effect engine operation. I am at a real disadvantage not being able to hear and/or feel the noise/vibration, it's real hard to say what the source is or could be. Just curious to know what you found out from GM?
Customer: replied 7 years ago.

We have not heard from the GM Field Engineer.


Aren't we entitled to a report from the test drive?

We left a message and asked the Customer Service rep who coordinated the test drive for the test drive report and/or for the test drive Diagnostic Scan Report - but they have not responded to us.


Aren't we entitled to it?


Why would AFM cause such problems if disengaged since I have so many problems with it engaged? Remember, I said the Engineer did something during the scanning and the noise/vibrations suddenly disappeared and the Engineer asked me if I noticed the difference and I agreed I did.


I would really like to have that report! How do I go about getting it?

I am not sure what kind of report will be available. I would say your best course of action is to remain again persistent but not overbearing with GM Customer Assistance. They will have direct contact with the needed resources to handle your problem from here. I really wish I had more to give you but I am afraid you have all the information I have available to me. Hopefully you have had contact with them since the last post here, and are closer to a resolution. I wish you and your family a safe and happy holiday season.


Please don't forget to ACCEPT your answer if you feel I have helped you. I do not get credit for the guidance I have provided unless you do. Thank You for using Just Answer.

Customer: replied 7 years ago.



In case you did not figure it out, GM came back with the verbal response that the case was closed for customer support and that the noise and vibrations were all due to AFM and all normal.


Yet, that day of the test drive -- they agreed it was a problem and was able to turn it off?!?!? And they have no report to forward to me to find out what they did!


I refused to accept that and continued to contact GM customer support as new developments of smell of burning and rattling rumbling began in the car.


Finally, the GM operations manager agreed we could take the car to a dealer of our choice. -- YOU already told us that cross warranty was a reality!


We finally found an engine expert who found the burning smell to be residual rubber which wore off and is now gone. He also found that the rattling rumbling was due to inproper installation at the factory -- a factory defect in the installation of the heat shield above the catalytic converter -- never tightened which the first dealership never found!


If you recall -- the GM bulletins you sent us -- that was ONE OF THEM!!! Finally someone knew what to look for and knew how to fix that!


The last problem is now the original roaring struggling noise of going uphill.


BUT -- the new dealership we are dealing with are willing to review the problem and the engine expert indicated that the damper placed by the original dealership was placed incorrectly on the vehicle.


You will not believe where it is -- in the front of the car on the top of the exhaust pipe ... instead of where the GM bulletin indicated -- of course, another ONE YOU GAVE US!

P.S. there is supposed to be 2 dampers and a strap and only 1 damper was put on.


They will correct this problem hopefully -- I have an appointment next week.


THE FINAL QUESTION I would like to ask is this:

Since the exhaust noise is right underneath the break pedal and going towards the door -- why would the bulletin indicate the dampers (2) and strap should have been put on in the rear anyway? Does this make sense? -- Is this true?


Let me know your final thoughts and/or comments.


And Merry Christmas and Happy Holidays to you and your family --

and the next correspondence will be our last!


Thanks for all your invaluable input. Still wish you were here!

Customer: replied 7 years ago.



Hope you get this.

As we talked earlier the resonance is created by the engine and transfered into other parts of the truck. As these parts vibrate or resonate they pass the vibration on to all of the parts of the vehicle they touch. The reason you feel the vibration in the floor board and brake pedal is due to the transfer path of the vibration, from the engine to the exhaust to the under body to the brake pedal etc.... The dampeners are placed in the exhaust to change its natural resonance and help decrease the transfered vibration into the floorboard by absorbing some of the vibration. The dampeners need to be placed at a point in the exhaust where the maximum resonance is found, which is commonly in the rear of the vehicle. And secondly the fit of the exhaust to the under side of the truck usually don't allow a lot of space anywhere else to place the dampeners.
GMKindl and 5 other GM Specialists are ready to help you
Customer: replied 7 years ago.



You have been such an invaluable asset of information for us. Thank you for everything.


You are definitely a die-hard GM man and everything you said has been straight forward and honest and correct.

ALL the info you gave has proven to be accurate and true and we cannot thank you enough for giving us a peace of mind as well as all the facts we needed. We just had to get others to simply follow.


We are very disappointed that GM is not standing behind its car as it should -- but at least we are now with a user friendly dealer. And just to let you know, the engine expert we found is another die-hard GM man (Nascar Earnhardt all the way).


2 out of our 3 car problems have been resolved -- and we will remain persistent and persevere until the final (the original) problem is also resolved.


Thank you for all the info on the cross warranty, the heat shield, the damper, the exhaust, the AFM, etc etc etc.


We are accepting at this point so that you can get your bonus for all you have done for us -- (short of being here to actually fix the car!). IF you don't get your bonus of $100.00, please contact us at our store email address: [email protected]. Feel free to contact us any time. We have been very pleased knowing you were there for us.


We are sincerely XXXXX XXXXX you -- you are what GM should always be -- reliable, dependable, knowledgeable, dedicated and committed to customer satisfaction.



Thank you.

John and Angela

Thank you for the accept and the bonus. As of yet the bonus has not been processed, or at least I have not been notified of the bonus. I will forward the information on to our customer service department. The site rules do not allow for personal information to be posted, so all of our communication is limited to this forum. Again I want to thank you and wish you and your family a happy holiday season.