What oil is best for my rear diif????

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Oct 1, 2007 | 04:27 PM

mikenews

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From: Buffalo NY

What oil is best for my rear diif????

I have a 98 z28 A4 that I wanna change the fluid in the rear diif. I believe I'm gonna use 75w-90w. My question is what brand of oil and do I have to add additive. I will most defiantly be putting in some sort of synthetic. I have had good experiences with Amsoil products before. What do u guys suggest??? Thanks

Oct 1, 2007 | 05:02 PM

3rdgentug

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From: memphis, tennessee

if you have an auburn ( clutch style ) diff. use an additive
if you have the zexel ( metal ) diff. dont use the additive

Oct 1, 2007 | 05:10 PM

dailydriver

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If you still have the Auburn (the stock unit, if you, or no one else changed it out) in there, DO NOT use synthetic!!!!(despite what ever the manual says) Use a good mineral based gear oil (Torco RGO, Lucas non-synthetic, Shaeffers, etc.) and start with 4 ounces of the friction modifier. Add more if there is still chatter after it is thoroughly mixed.

Oct 1, 2007 | 08:18 PM

chicane

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Dont use a synthetic... period. Honestly... what do you actually gain from running it ??

Nothing... comes to mind.

Seriously though, you woud gain more from stepping up to an 85/140 or a straight weight 140 than you would from changing over to a full syn. Personally, I am a fan of the parrifin based oil from Schaffer... and dyno based from the like of TORCO... and then add friciton modifier to taste.

Oct 6, 2007 | 08:33 PM

mikenews

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Where do I get the friction modifier? GM dealer or can I buy some from parts store?

Oct 6, 2007 | 10:15 PM

alamantia

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From: NJ

either

Oct 6, 2007 | 11:23 PM

8a8mfh

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Quote:

Originally Posted by mikenews

Where do I get the friction modifier? GM dealer or can I buy some from parts store?

GM or ford ONLY.
I had two tubes , 32 oz, of the parts store crap in my first new Auburn and it made all kinds of noises. Called Auburn, they said thats the one question they get 20 times a week, all related to cheap friction modifier.
I ended up getting GM gear oil and ford friction modifier because GM was out.
4oz of the good stuff stopped all the noises.