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Doug
Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 6924
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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Mitsubishi Montero Limited: 2002 Montero Limited; 119k miles;

Customer Question

2002 Montero Limited; 119k miles; owned since new and very well maintained.
Have developed a vibration/low rumble. seem to be coming from the drive-line toward rear; speeds above 40 and especially on the highway. Rumble is only with slight+ power on gas, goes away immediately on coast and decel. Rumble frequency seems same even with speed change
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.
Hi,
How long has this situation been occurring, in miles?
Customer: replied 1 year ago.
Hard to say - the truck is driven mostly city driving, the New England winter did not see bare roads until March - at least since December or for about 5000 mi....I think this has been there but became more noticeable - the reason why I am concerned is that I have been driving more highway and it has become an annoyance and noticeable to passengers. It really sounds like a tire thump issue but I jacked up the back end, tires off the ground, ran it up and it seems to still be evident. Was going to take it to the dealer, but at $120/hr I thought I would reach out.
Expert:  Doug replied 1 year ago.
Thanks.
When the noise/problem is occurring, it is fairly rapid effect, similar to driving over rumble strips on the shoulder of the highway?
Customer: replied 1 year ago.
No where near the intensity of a rumble strip. Very low amplitude 1/rev wheel speed. Very suttle in vibration (most would not even notice), more noticeable in noise, but also very suttle. At 50-70+mph, windows closed can bring it on as gas is applied, does not take a lot of load. Let off the gas and both vibration and noise virtually go away. I suspected the tires but letting off the gas a noisy tire in my experience stays somewhat noisy. I did switch tires from noisy Yokohama A/T to quieter Yokohama H/T. I am so tuned in now most may not even notice.It feels mechanical in the drive train and but is not typical bearing type noise. It just feels there is a suttle shake in the whole system.Based on the engine load/unload, could it be engine driven, the RPM range of the issue is approximately 2 - 3000 RPM. Is there any checks I should do in Neutral either parked of at speed?
Expert:  Doug replied 1 year ago.
Thanks.
Given the symptoms it sounds more like a tire issue than anything else if not for the letting off the gas part, as you mentioned they usually stay a little noisy until out of that range.
Do you have the selectable gear transmission? And if so, does the vibration/noise change any if you drop a gear at for example 40mph? Like getting louder/faster, going away, etc?
Customer: replied 1 year ago.
I do have the 5 speed but I have not tried any experiments other than using it in a manual mode and seeing the same issue as automatic. I do not detect a change in the condition based on engine RPM change, although winding it through 3rd and 4th gear, the engine noise makes it hard to hear/feel the drive train.Here is what I will do, I have a new OEM spare tire that I know is good and quiet, I can switch it starting LR where I think the noise is stronger, then RR to see if there is any change. After that, I also thought about rotating the drive shaft 180 degrees at the diff to see if there is a signature change. Does that make sense? I can get back to you next week.
Expert:  Doug replied 1 year ago.
That sounds like a pretty decent plan. Lets go ahead and do that moving it from position to position to see if you influence the noise any.
The drive shaft you shouldn't need to worry about. If you have the one piece unit then bolting it in different positions will have no change...if you have the two piece unit you will throw it out of balance by rotating the two shafts. Unless you see something obvious like a spot where a weight rusted off etc, there is no reason to suspect the shaft somehow got out of phase etc.