Differential noise?
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,885
Likes: 260
From: Hillsboro OR
Differential noise?
I have an 2003, A4, Coupe with a 2:73 rear-end. I bought it last June when it had 14,7000 miles on it. About three months later (~17,700 mi.) I was getting a low growl/grind/clatter noise on slow hard turns (pulling in/out of parking spots,driveways). I went to the dealer and they did a rear diff "service". I assume they changed or top off the fluid and added the positraction additive. Now it's six months later and the noises are back and getting louder. I don't see any oil spots on my garage floor and haven't see any signs of a leak. Is the rear-end going out?
This car was a "GM Certified" used car and I took it to the dealer for this literally 17 miles after that warranty ended.
The dealer serviced the differential still under warranty but they had to be coaxed. 
Do I get a warranty on the serviced they performed? (i.e. 12 months/12,00 miles)? Am I buying a new diff? I good news is that I want to change to a 3:42, 
but my wallet was hoping i could wait a few months. Sorry for the long post but, I could sure use some of that good CF advice. Thanks
Randy
This car was a "GM Certified" used car and I took it to the dealer for this literally 17 miles after that warranty ended.
The dealer serviced the differential still under warranty but they had to be coaxed. Do I get a warranty on the serviced they performed? (i.e. 12 months/12,00 miles)? Am I buying a new diff? I good news is that I want to change to a 3:42, but my wallet was hoping i could wait a few months. Sorry for the long post but, I could sure use some of that good CF advice. Thanks Randy
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
A common differential noise is the hallf shafts sticking inside the wheel hub. It's splined, and it slides in and out. They rust up and try to stick, then they break lose and pop and creek. If that is the problem, then it just needs to be lubricated.
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,885
Likes: 260
From: Hillsboro OR
Thank you for the reply. It it a major job lubricating them?
Le Mans Master
Joined: Aug 2000
Posts: 5,808
Likes: 1
From: Sierra Foothills California
I had exactly the same scenario. Took the car in because of the small leak on the drivers side diff. cover. After another 15K miles it started getting noisy. I thought they'd forgotten the friction modifier. They tore into it and found the pinion bearing and one carrier bearing bad. The dealer said they'd rather replace the rear end than repair it, but it was up to GMPP (extended warranty) After looking at it they replaced it with new. I was a "happy camper" Oh, it was already a 3:42 
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
There was a thead on here just last week I think about it. Take the wheel off, and take off the center nut. Spray some penitrating oil inside, and from behind. The best way is to remove it and grease it, but a lot of people say the penitrating oil works.
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Instructor
Joined: Sep 2006
Posts: 214
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From: OR
Thread Starter
Le Mans Master
Joined: May 2006
Posts: 7,885
Likes: 260
From: Hillsboro OR
Updated
I had the dealership change the diff. fluid and put in Mobil1 75/90 Synth w/ the LSD additive. and the rear-end noise is gone again. They told me there were some thin metal flakes floating in the old oil. I am still going to replace it with the 3:42's later this year. I now just have a little more time to work up the cash.
