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gm additive
Launching!
Joined: Mar 2004
Posts: 213
Likes: 0
black00TA...you are correct. The Torsens (99 and up) need synthetic and the Auburns (98 and older) are not supposed to have synthetic. The Auburns use friction clutches that the synthetic messes up, but they NEED the friction modifier additive. The Torsens use spider gears so synthetic keeps them quieter, although mine clunks all the time anyway. The additive is optional for Torsens.
i didnt use the additive the first time i changed the fluid on my first rear-end and shortly after it was grinding every once in a while that i could hear. soon as i added the additive it went away. but my rear-end was shot soon after =]
Launching!
Joined: Mar 2004
Posts: 213
Likes: 0
I just took out the entire GM service manual for 1999 F-bodies from the library. It says for both posi and open diffs to use 75W-90 synthetic and for all posi to add the GM additive. So I guess the Torsens are supposed to have it too, since 1999 was all Torsen for posi.
I do not understand why you would need the additive if there are no clutches. There is no need to enhance friction, in fact you want less on the Torsens since they are all gears. It would be like putting that auto tranny clutch pack enhancement gew in a manual.
Launching!
Joined: Mar 2004
Posts: 213
Likes: 0
That's what the GM factory manual says. What I have heard is that they add it to reduce noise. Some Torsens have a "rusty screw" type noise that the additive supposedly helps. Other than that I don't know. I put the additive in my Torsen and it works fine.
We need to get more opinions on this. The manuals might not be up to date. I will ceck mine. I just put new fluid in my rear and if I need the additive I need to know soon as I will be driving the car tonight first time since October.
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On The Tree
Joined: Jan 2004
Posts: 158
Likes: 0
From: El Paso TX
Originally Posted by blkbird
I just changed my fluid about 2.5k ago and now i can hear a whinning. Any idea if that is because of not adding the additive??? Its an 01.
Yes, I changed the fluid on the rear and did not do the additive. I started whinning but stopped after the additive was added. Mobil one requires the additive then, right?
according to FIREHAWK#608 mobil1 has it already.....i changed my fluid about 3.5k ago (with mobil1) and DIDNT USE THE ADDITVE....havent gotten a whine yet...done a few races with it too 
