Differential chatter...
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Le Mans Master
Joined: Mar 2007
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From: Charlotte NoCar
National Champs Gators 4 St. Jude '09
St. Jude Donor '10-'11
Differential chatter...
I have a 2000 Coupe A4 with a noisy/chattering rearend. From research, I\'ve narrowed it down to the differential and its need for some friction modifier (thanks in large part to RevXtreme). My questions are: I know the GM PosiLube is an additive, but do I need to change all the fluid in order to add it? Also, I don\'t know if I can get my hands on the GM part...are there an additive and a diff fluid recommended that I can buy at Advance Auto Parts or Napa? Any help is greatly appreciated, I know there are smarter people than me out there...
Le Mans Master
Joined: May 2006
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From: Hillsboro OR
Change the gear lube too. I bought the gear lube at autozone and the LSD additive at the car dealer. After the fluid is changed find a parking lot and do very slow figure-eights, forward and backwards to work it into the clutches. 
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Le Mans Master
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From: Charlotte NoCar
National Champs Gators 4 St. Jude '09
St. Jude Donor '10-'11
Thanks for the input. I just found both GM lube and additive on Ecklers\' site and ordered them...now to read a few threads on actually changing the fluid!
Safety Car
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From: Ocean Springs MS
Racer
Joined: Dec 2005
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From: bloomington Indiana
I had a chatter on my 99 vert when making tight right turns (the right rear would chatter) that I thought was diff. It ended up being a bad RR shock that had no "resistance" in the last 2 inches of travel.
After removing the shock from the vette, you could collapse the shock and hear air bubbling, and while extending, the last part of the stroke basically felt like no oil was in the shock.
After removing the shock from the vette, you could collapse the shock and hear air bubbling, and while extending, the last part of the stroke basically felt like no oil was in the shock.
Instructor
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From: Gardner KS
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Le Mans Master
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From: Charlotte NoCar
National Champs Gators 4 St. Jude '09
St. Jude Donor '10-'11
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Le Mans Master
Joined: May 2006
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From: Hillsboro OR
Jack the car up level (front and rear). After it's drained, pour in one quart. Then add the additive. finally, pour in the other quart (you will only need 1/2 to 3/4 of the second quart before it's full. 
Le Mans Master
Joined: May 2006
Posts: 7,826
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From: Hillsboro OR
Jack the car up level (front and rear). After it's drained, pour in one quart. Then add the additive. finally, pour in the other quart (you will only need 1/2 to 3/4 of the second quart before it's full.
Definitely, do the slow figure-eights. I did 2 forward and 2 backwards. No more noise.
Definitely, do the slow figure-eights. I did 2 forward and 2 backwards. No more noise.
Safety Car
Joined: Jul 2001
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From: Ocean Springs MS
Instructor
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From: burlington ont
i just did mine, this is how i did it. i jacked the car up from the back, unscrewed the drain plug, lowered the car back down, waited until the fluid drained, jucked the car up and tightened the plug(35 N-m or 26 lb ft) and lowered the car back down, took off the fill plug and filled it using a transfer pump that i bought from wal-mart. after it was full of gear oil and stabilizer, i put the fill plug back on and tightened it(35 N-m or 26 lb ft) then i took it out and did the slow figure eights. good luck.
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Le Mans Master
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From: Charlotte NoCar
National Champs Gators 4 St. Jude '09
St. Jude Donor '10-'11
Thanks for the input guys. I\\\'ve got all my supplies and I\\\'m gonna do it really soon. It\\\'s funny...I can work on the engine, rip the interior apart to install/fix various things, but I\\\'m nervous about draining my diff...I guess I just gotta get in there and do it! Would be a great challenge for me if I ever get on Fear Factor 