03 Explorer XLT Rear Differential

[explore34]

In the changing fluids section, it says to add Ford's friction modifier to the rear diff fluid. If you use synthetic fluid, do you still need to add the friction modifier? Any replies, thanks.

 

[coled43]

I think it depends on the particular brand of fluid. I have seen it printed on the bottle for Royal Purple that friction modifer is not needed. Most places sell some type of aftermarket additive that should meet ford specs. You only need it if you have a limited slip differential though. If you don't know, there is a code on the door pillar that you can lookup somewhere on the site.