GM recommends 80w, 80W90 GL5 gear lube, + GM additive #1052271 for limited slip differentials for my KITT I want to use Royal Purple 75w90 Gear lube to my rear end, will it screw up my rear end? Should I add the additive or not? or use something else?

Hi:

It will not hurt the rear End. Just stay with the same weight that GM Recommends. I

I had used the Royal Purple Gear oil before in my 85 Trans Am with Australian 9 Bolt Rear End, it was good. I did not add any other additives. I have since switched to Amsoil Gear Oil for the Rear End.

I have been using Amsoil Syntheic Oils in the engine and their products seem to work very well my cars. Just a personal thing I guess.

Thanks
Rob