Ok, I have been doing lots of research on the forums on what fluid I should use for the rear differential. My manual says 80-90w and other people say 75-140w. I would really like to get the Royal Purple 75-140w but I am not sure which to get. I got the 12 bolt cap. Also I know I still have to add the modifier.
Please any information is appreciated.

 

I want to say I used the 75w90 valvoline oil in mine.

 

Or I don't if I should go with 75w-90 Royal Purple.

 

Honestly I don't see it making much of a difference in terms of lubrication. I'd personally stick with the 75w90 just because I don't think there's going to be much benefit in running oil as thick as a 140 weight.

 

Im thinking of just going with the 75w-90

 

the 140 would be better if its a tow rig, otherwise you shouldnt be generating enough heat in the rear end to worry about. however if you still have the owners manual, just put in whatever it specifies, they did change the callout based on installed equipment in the truck (tow package, which rear end, LSD ect)