So I'm putting in my new transmission and going to change my rear end gear oil, so should I use regular Valvoline 80w-90w GL-5 with the Trans-X GM additive or LUCAS heavy duty 80w-90w that apparently does not require the additive since it is pre-mixed? Stock 10-bolt Rear with Stock 3.23posi-tract Gears, 172,xxx miles!

 

Generally speaking, there is no substitute for the genuine GM LSA. Most other LSAs don't seem work like it does.

 

Ok, thanks for the info, already went with the regular oil and the additive mentioned above, will get the GM additive next time if I have any problems, I have used it before but, not a GM product, same type rear end though.