A few months back, Arthur Margotta put up a post about 2003 Chevrolet Avalanche that was run low on gear oil, and now has a "gear noise". From his initial post --

>If anyone has had this type >of problem please let me know on all types of fixes short of >replacing ring & pinion gears. Note: All the bearings are OK >& have not been damaged in any way by the low oil condition.

I'm not sure why this post struck a chord with me, but it did. Actually I do know why…The only posts deemed helpful by Arthur, had nothing to do with addressing the source of the noise, but had to do with 'fixing' this with inexpensive techniques. I can't comment on using Crest to quiet down a noisy gear set, but I can say this will not address the root cause of his rear differential noise, and that if it did work, it was a temporary measure.

I've done some differentials since that post, but this one I'm currently working on is a good example of what may have happened on Arthur's Avalanche.

A customer brings in his 2008 Silverado. It's a half ton with a 8.6 rear differential. It has a little over 170,000 miles on it. He requested a rear end service. I asked if it was maintenance, or was there a problem that needed to be looked at. No problems…OK

I road tested the vehicle. I noticed a noise when turning left that went away when turning the right. This wasn't heard going straight. On a coast/deceleration there was gear noise heard from the Ring & Pinion gears that went away accelerating. I call the customer up…Yeah, it's been doing that for about a year. Um…OK

No leaks were seen and the differential was filled. I removed the inspection cover.

This is what I saw. [2008 Chevrolet Silverado 1500 LS, Photo] Looks good, right? That is until I looked a little closer. [2008 Chevrolet Silverado 1500 LS, Photo] And here [2008 Chevrolet Silverado 1500 LS, Photo]

Tip - Removing pinion yoke [2008 Chevrolet Silverado 1500 LS, Photo] Taking this apart I see the following - [2008 Chevrolet Silverado 1500 LS, Photo] [2008 Chevrolet Silverado 1500 LS, Photo]

Another tip I'd like to point out after doing rear ends for a few years is the complaint of noise if reusing the gears. I've had a few differentials that had bearing noise, but when I was done there was a problem setting them up. What did I do? I thought I didn't change the set-up? Or did I?...

Pay attention when removing the old races. Clean up the area(s) with a burr or dremel tool.[2008 Chevrolet Silverado 1500 LS, Photo]

Same on the case after removing the side bearings. [2008 Chevrolet Silverado 1500 LS, Photo]

Tool tip - Case spreader. I had one on this truck, but it was not needed as the case came out of the housing easily. Putting this back together it will definitely be of help.

Differential Set-Up Tips For the 8.6 rear end - GM PIP3720D

Finally, going back to a rear end that was quiet from day 1 until now. I stand by my statements to Arthur, something changed to cause the noise. I'm not sure why we want to be hero's when we should be fixing things and making money, but...

Scott from California

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