My 4th Gen 10 Bolt Posi Rear on my 91 Z28 is leaking fluid. The car has barely been driven since I had the Motive 3:73 gears installed a few years back. Either they didn't use enough RTV or the Paper Gasket along with the RTV isn't working together too well. I plan to just reseal it with RTV only this time. I just got back from Autozone where I got two bottles of the Valvoline 80W-90 Gear oil (Not synthetic) that says "Limited Slip" right on the bottle. I also got ripped off at the dealer (IMO) for $18.xx on the 4oz bottle of the GM Limited Slip Additive. I just wanted to make sure, do I still use the additive since the gear oil says Limited Slip on it already? Thanks!

 

The additive helps the clutches to be smooth around corners. If the lube already has it, its not a good as GM/ford additive, lil extra wont hurt.

 

That's kinda what I figured. At first I wasn't going to go to the dealer, then I did and almost didn't buy it because of the ridiculous price, but I said the hell with it and bought it anyway. Thanks.

 

Read the fine print on the gear lube carefully!!! It probably says something like "compatible with" or "meets specs for" or some kind of weasel-wording like that; which is NOT the same as, "already contains additive".

You still need the stinky juice from GM.