I've read in a couple places that Ford now recommends 75W-140 synthetic gear lube in the rear differential instead of the 75w-90 synthetic. Is this true?
My owners manual says to use 75w-90 synthetic.
The Haynes maintenance manual says to use 75w-140 synthetic.

Also, I've got a 9.75" limited slip so I need to use some friction modifier.
My owners manual says to use 4oz of XL-7 friction modifier.
The Haynes maintenance manual says to use 8oz XL-3 friction modifier

Anyone know which is correct? Whats the difference between XL-3 vs XL-7 friction modifier?

Thanks.

 

Rear Differential Maintenance:
75W-90 or 75w-140?
friction modifier XL-3 or XL-7?
add 4oz or 8oz of friction modifier?

Anyone?

 

I asked the same question myself. So I called the dealer and asked. He said the 75/90 with 4oz of friction modifier.

 

thanks for the reply. I'll check with my local Ford dealer as well and post their answer.
Seems there are two types of friction modifier...XL-3 and XL-7. I've got two different references one stating to use XL-3 the other XL-7.

 

Unless you have had your diffs underwater ford says they need no maintanence for the life of the vehicle.

 

anybody find some news on this subject.