WHAT FLUIDS DO I NEED TO PUT IN MY FRONT AND REAR DIFFS ON A 1992 F-250 4X4? HOW MUCH IN EACH? HOW MUCH FRICTION MODIFIER? I'M NOT SURE WHICH DIFFS I HAVE? CAN ANYONE HELP ME? WHAT SHOULD I USE FOR HYPOID? WHAT IS HYPOID? IS THERE A COMMON NAME FOR IT? PLEASE HELP. THANKS

 

I kind of need to know the same thing, not sure how to tell if I have a posi rear diff, how do you tell? hey MCalvin460CI if we don't get a reply try your local ford dealer, there pretty good about giving answers to theses kind of questions

 

Both of you can find all that info & more in a Haynes manual.

"Hypoid" gears are spiral-cut. They're much stronger & quieter than "bevel" or "spur" gears whose teeth run straight, but they all use the same gear oil.

This page shows how to tell if you have a limited slip - only GMs have "posi"s.

BTW Calvin - turn off the ALLCAPS.

 

thanks steve, I have a 3.55 LS do I have to add the diff additive to the gear oil?

 

Yes.