Fluid for diffs?

[Lancaster]

Any recommended fluid for front and rear diffs? I know it needs to be 75-90. I have the locking rear diff. Seems like valvaline synthetic is popular. Please let me know what you recommend.

 

[RCB]

I used Royal Purple during my last diff service but I think it's overkill cost wise. I always use Moblie 1 or Valvoline Syn. for my customers with no issue and will go that route for my own truck next time.

 

[malones99]

Why are you changing the fluid?