I have a 99 Z28 with 3.23's. I want to change the diff fluid but I don't know if the limited slip additive is required for my rear. Also what is the proper weight gear lube to use? Synthetic? Any brands I should stay away from?

Thanks to anyone that can help!

 

80W 90 GL5 or equivelent, I've never personally had any problems with just the basic brands you commonly find.

you will need the GM limited slip additive, otherwise your rear will be very unhappy

 

I've had good luck with Mobil 1 gear lube and GM limited slip additive. They only sell one weight of M1 gear lube around here but I think it's 80w90.

As has been said if you don't use the limited slip additive your rear end will hate you.