Ok, I'll be changing out my differential fluid this weekend. It's a 1991 GTA with the factory 10-bolt. I bought the GM additive and 3 bottles of rear gear oil from the dealership. I also have the gasket for it. Now, how much of the rear gear additive do I use, the whole bottle? And how much fluid do I put in there? 2 quarts or all 3? TIA

 

Fill it to the fill plug hole. Or until you can touch the fuild with your finger though the fill hole.

 

How big of a bottle of additive did you get? Should hold about 2 quarts, like he said fill to the fill hole.