Differental Fluid Question
Thread Starter
Burning Brakes
Joined: Jul 2007
Posts: 1,078
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From: Pomona, New York
Differental Fluid Question
Just put a new 3.90 rear in my car and the gentelman tha tbuilt it said put the OEM gear oil in. I went to the GM dealer and bought 3 quarts of what the parts manager said came stock in the c5. After reading some threads here i noticed that people are putting a limited slip addative in which i did not. Am i ok or am i supposed to add something else. The bottle i added reads..... Synthetic Axle Lubricant SAE 75w-90. Nothing on the bottle about addative. Thanks for the help.
Melting Slicks
Joined: Aug 2007
Posts: 2,721
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From: Elizabethtown
Pro
Joined: Jun 2008
Posts: 516
Likes: 6
From: Spartanburg South Carolina
Have you done any engine mods yet? I have H/C/I, and was told that gears will feel like I had that done all over again.
Thread Starter
Burning Brakes
Joined: Jul 2007
Posts: 1,078
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From: Pomona, New York
Car has turbos. Makes 525 at the tire. I like the gears but i think the 3.42 were better for turbo. My quatermile time was almost exactly the same with the new 3.90s and slicks compared to the 3.42s and street tires. Im pissed.
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Pro
Joined: Jun 2008
Posts: 516
Likes: 6
From: Spartanburg South Carolina
I had always read that FI cars did better with 3:42's and less.
You should post about this over in the performance section. A lot of good guys over there that could probably help you figure out why this happened as there are a lot of variables involved.
Team Owner
Joined: May 2006
Posts: 21,473
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From: Palmdale, Ca----- 2009 Cyber Gray 4LT A6 F55 452 RWHP 422 RWTQ- RIP 1998 C5 734 RWHP & 585 RWTQ-----
I'm am glad to see you added the additive - you would not of enjoyed the resulting damage to your new 3.90's! 
Enjoy and be careful
Thanks,Matt
Enjoy and be careful
Thanks,Matt
Racer
Joined: Dec 2007
Posts: 354
Likes: 4
From: Grand Ledge Michigan
You will chatter eventually with straight gear oil, and soon, and could damage the differential, it needs to slip a bit around corners because the outside tire travels farther than the inside tire, enough corners and you can do damage without the slip additive (friction modifier) the the Corvette is designed to have.
Your parts guy is an idiot, get a new one, he doesn't know jack about Corvettes....
Your parts guy is an idiot, get a new one, he doesn't know jack about Corvettes....
Team Owner
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From: Canon City Co
St. Jude Donor '11,'13
"I voluntarily took 60 days off from OT"
Burning Brakes
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From: Waunakee Wisconsin
St. Jude Donor '20
Team Owner
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From: Canon City Co
St. Jude Donor '11,'13
"I voluntarily took 60 days off from OT"
Le Mans Master
Joined: May 2005
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From: Fort Lauderdale, Florida
The most recent version of GM's rear end synthetic lube does not require additional posi lube, it is built into the new fluid. The part # is GM 88862624 or AC # 88862625. Dan, you should have known of this because I think Bruce or someone else posted it a while ago on the C5registry.
Team Owner
Joined: Mar 2008
Posts: 24,310
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From: Canon City Co
St. Jude Donor '11,'13
"I voluntarily took 60 days off from OT"
The most recent version of GM's rear end synthetic lube does not require additional posi lube, it is built into the new fluid. The part # is GM 88862624 or AC # 88862625. Dan, you should have known of this because I think Bruce or someone else posted it a while ago on the C5registry.