I want to change the fluid on my recently rebuilt GM corp 8.5 with new Eaton posi carrier. The builder used a real thick 140 I think viscosity. I want to use a stock viscosity 85-90 I think to reduce HP loss from drag. I will be using GM posi additive as well. Eaton says not to use synthetic. Was thinking of using Castrol Typoid. Any other suggestions?
i would think any good 90wt oil and the gm additive would be all a guy would need.of course i think some guys run redline or royal purple if you want to spend more money.
Valvoline 80-90 or Coatal 80-90 is what what I usually buy. For posi additive I only use GM limited slip additive. Buy it by the case. :3gears: Roger
Bought several 5 gal pails of SunVis (Sunoco) 85-140 in the 90's. Used to offer it to r/e customers instead of really expensive Redline. The Dana70 in my Cummins Dodge runs the SunVis 85-140 synthetic...no problems. I change it every 30K. :3gears: Roger
Thanks for the info. Also a friend of mine who is an old time GM mechanic told me that the old rear diff fluid had whale oil in it! This was discontinued back in the early 70's he thought. He said this is why they did not use posi additive back then. Crazy! I bet the whales are thankful
