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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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02 duramax. Grinds and has difficulty getting into 4WD.

Customer Question

02 duramax. Grinds and has difficulty getting into 4WD.
Submitted: 1 year ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 1 year ago.

HI there, I am Cam. Can you tell me if the noise is in the front axle or the transfer case?

Customer: replied 1 year ago.
No, but that's exactly what I am trying to figure out. Person that rebuilt my T-case said to remove front driveshaft and test again (thinking it may be front pinion bearings). T-case is under warranty so I'm not sure if he's passing the buck. If I remove front driveshaft, drive, and still get the grinding when engaging 4WD (ONLY when engaging), what does that tell me. If it goes away, what does it tell me?
Expert:  GM Tech (Cam) replied 1 year ago.

As much as that’s good,it won't rule anything out. Taking out the shaft will cause everything to be unloaded. What you are going to need is to listen carefully under the vehicle while its being shifted to see.

Can you also tell me what speed you are shifting at?

Customer: replied 1 year ago.
Effort to get into 4WD varies. Grinding is louder and more severe (I can actually feel it in the cab) the faster I go. Sometimes it takes just a second to engage 4wd. Other times it take a few minutes of driving. I haven't figured out a repeatable pattern. Couple times it seems like backing up helped, but again this doesn't always help. No grinding when at a stop of course, but doesn't always engage right away when stopped. Shift speed is anywhere between 0-55 mph (mostly 5-15mph). Always grinds into 4WD when truck is moving (even 1 mph). Not sure how I'm going to listen under the truck when it's moving.
Customer: replied 1 year ago.
Would putting truck on 4 jackstands tell me anything? Maybe where a helper engages 4WD while I'm (safely) listening underneath?
Customer: replied 1 year ago.
If the noise is from the front diff, what part of the diff is expected to be bad? If the noise is from the T-case, is syncros the only cause?
Customer: replied 1 year ago.
I should also say that when I changed the T-case, I replaced all suspension and steering components on the front drive corner of truck. Tried to get axle fronge out of diff with slide hammer and it would not come out (even turning occasionally and jerking to center snap ring). Never got axle flange out. Gave up after I BROKE a slide hammer.
Customer: replied 1 year ago.
Front driver side corner I meant to say.
Expert:  GM Tech (Cam) replied 1 year ago.

Sorry I was in the washroom.

If the front diff is the issue, the axle that slides to engage the front axle is the issue. The gear slides to connect the 2 parts of the axle.

IF the transfer case then it could be tire.

You also need to check the circumference of the tires. In a flat parking lot make a mark at the very bottom of the tire. Then drive ahead 1 full turn of the tire until the left front is back at the very bottom. Then compare the marks. All must be with in 1 inch. More than that will cause issues in the transfer case.

Customer: replied 1 year ago.
Do you have a diagram of the front diff assembly so I can understand what you are talking about with the sliding parts?What did you say about the transfer case?
Expert:  GM Tech (Cam) replied 1 year ago.

Based on the fact you say its worse with speed, that tells me it may be tires. WE need to check, the circumference of each using the method I mentioned.

Customer: replied 1 year ago.
I will start there with circumference. Also buying all new tires Friday. I will report my finding and we can go from there. Stay tuned.
Customer: replied 1 year ago.
Problem is 10 times worse at 45mph compared to 5mph.
Expert:  GM Tech (Cam) replied 1 year ago.

It would be best to reconnect after friday then ask that usually rules the issue out.

Customer: replied 1 year ago.
Measurements were within 5/8". Trying to mount new tires tonight.
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, let me know.

Customer: replied 1 year ago.
New tires did not fix the problem.
Expert:  GM Tech (Cam) replied 1 year ago.

OK so the next step is to remove the front right axle assembly and check out that sliding gear.

Customer: replied 1 year ago.
Can I get an exploded diff assy diagram so I know what I'm looking at?
Expert:  GM Tech (Cam) replied 1 year ago.

Items 5-15.

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