Fluid for my rear-end

[ILLEGAL69]

I have a question about the fluid in the rear-end of my truck.
I have a 2000 Ford F-150. The tag on the axle says to use 75-140 synthetic. I have read that the 75-140 is not recomended by some Ford techs.
Should I use 80-90 Amsoil with the Ford friction modifier?
Should I use 75-140 Ford with the Ford friction modifier?

[ballistic69]

I have Amsoil 75w-140 in my 2001 Super Duty in both front and rear diffs. :icon996:

[dennis68]

We use 75W-140 synthetic on ALL our locker style diffs at the Dodge/Jeep shop.

[ILLEGAL69]

Right on, thanks for the info.

I bought the Amsoil 75/140 today. I was going to use that with the Ford friction modifier.