sonoma43

iTrader: (1)

Whats everyone runnin for rear end diff. fluid?
It's about time to change mine out and was goin to go with either Lucas or Royal Purple but I have the factory rear end with G80 3.73's IIRC GM call's for semi-synthetic?? Whats the best to use?

viciousknid

iTrader: (8)

I don't think brand matters much with rearened fluid. Just make sure you run whatever viscosity they call for.

GMCtrk

iTrader: (27)

i put in 75w90 castroil or whatever it is they sell at autozone.

AKlowriderZ71

iTrader: (22)

GM recommends synthetic 75w-90. You can choose the brand.

sonoma43

iTrader: (1)

Thanks for the info guy's! I'll be changing front and rear very soon, I guess I will run Royal Purple since it is actually the cheapest comparitive to other at my local autozone.

budhayes3

iTrader: (19)

Yea, the factory G80 calls for synthetic 75w-90, whatever brand you prefer

TexasPainter

iTrader: (1)

Redline

Parke10

iTrader: (5)

factory g80's dont need any additives do they? im stuck between castrol,mobil 1 and royal purple.

budhayes3

iTrader: (19)

Nope, no additive, just syn 75w-90. I went with Mobil1 myself last time out.

Oldcrow

I used Amsoil 75w-90
Put the same thing in the front diff