can I use Royal purple 75W-90 in the rear end diff on my 2000 f150? it has a JLP 4:10 gear set installed. thanks.

 

I'm thinking you'd need the 75-140 stuff, that's what originally it came with. I run the 75-90 in my muscle car, but it has a locker, 650hp and 35 splined axles.

Someone else might be able to elaborate a bit more on the differences.

 

Ford has changed the specs to 75w140, and if you have a LS, make sure you use friction modifier.

 

Ford has always spec'd 75W140 for the rear...the change was to now recommend 75W140 for the front as well; as opposed to the old spec of 75W90 for the front.

You should run 75W140 in the rear.

 

Not correct. Check the 04 and up (and possibly earlier years) owners manual. Spec was for 75w90 in both. Ford later went to the 75w140 in the rear and 80w90 for the front, my guess is due to problems.

Right out of the 04 manual.

 

Run what JLP recommends. If they don't recommend a specific lube, run 75W140. If it has a factory limited slip, add a bottle of Ford modifier.

 

Ahhhh, cool. Thanks for the lesson. They must have swapped in '04 with the NBS. Didn't know that one.

 

X2