I'm almost ready to change my diff oil and inspect after my 500 mile break-in. I tow some and live in western PA. Eaton does not recomend synthetic gear oil, so I'm stuck with dino! What oil weight would you use and what brand? I'm thinking 85w140 because I tow alittle. But I live in western PA and it gets cold sometimes in the winter. Help me out!

 

Good ? I've been running the 85/140 in mine aprox 5,500 on it going to service it soon

 

Well, Factory calls for 75w-140 and hasn't segregated Canada from Florida as far as temperature reccomendations go(which is odd)
I would think 85w-140 is suitable if thats all you can get a hold of.

 

I asked exactly this question to Royal Purple.
They said, to run their 75w 140 which I have been doing with my 9.25" Detroit trutrac fitted rear for over 30 thousand mile now, with no problems.
Al.