2wd Rear end service for a 4 door LS
 

Do I need any additives for the rear fluid when I change the oil??

No. The additives in gear oil are friction enhancers. The open diff has no clutch material to benefit from the additives and if it's G 80, general motors and eaton (manufacturer) recommend not using any friction enhancers. If your trusted brand has additives, they won't damage anything. But if the ring and pinion guy tries to sell a little bottle of something to add, no thanks.

Thank you!!! My neighbor is trying to sell me amsoil with additional additives. Since this thing is stock right now, I don't want to be buying anything overkill for no reason.