Hey guys sure feels good to be back on this forum. My question is what fluid/oil type is recommended to run in the r151 transmission and rf1a transfer case? Thanks in advance

 

API GL−4 or GL−5 SAE 75W−90

 

It all depends in what part of the world .

The lower the temperature the thinner you run.

Here where it is not real cold I run 85 /140 for the last 10 or 15 years

It is a personal choice

 

The T-case is fine with GL-5 and I'm told the trans is fine with GL5 but, my R151F shifting was "notchy" when I ran GL-5.

It didn't shift smoothly into another gear. It kind of hesitated and you could feel slight bumping as if the gears weren't meshing as smoothly as they should. No grinding or anything harsh but, it was annoying.

Found some GL-4 and it shifts better. Many say this is bull and I didn't believe it either until I switched back.

This was the case before and after the trans was overhauled. I've run Redline and Sta-Lube GL-4 and it shifts great.

 

I live up in the heart of rocky mountains and it does get cold. I know what you mean about "notchy" i do feel that also so i was thinking of running lucas gear oil as an additive and maybe synthetic 75w90?

 

The RedLine oil is synthetic and rated as GL-4. The Sta-Lube is dyno GL-4.

"SUPPOSEDLY" a difference in lubricity or slickness between GL-4 and GL-5. I don't want to start any arguments about this issue. I'm not an oil engineer.

I did not believe any of it and just switched back to GL-4 in desperation. It cured the notchy shifting so now I'm a believer.

It wasn't related to cold weather. I'm in Az.

 

ok great thanks for the info