I just bought a 1992 4x4 F250 7.3. I cannot find a straight forward answer for what type of gear oil to put in the front.

The consensus seems to be 75w-140 for the rear differential. I have a 4:10 "conventional non-positraction differential" in the back so I guess that means it is not limited slip and does not require friction modifier. Any clarification would be helpful
Thanks
-John

 

Same oil 80w/90 or 75w/140. I like the heavier stuff, but to each thier own. If it were me, especially in a Ford. I would run synthetic in the rear and dyno in the front.

 

What are the capacities for the front and rear diff's. I have 4x4`94 F350 with a 4.10 LS. I will run the 75-140 synthetic in both just so I will only have to stock one type of lube. I understand a LS additive will be needed in the rear. Stinky googy stuff. Is there a more specific name for the additive?

 

Thanks a lot!
As far as I know, all 75w140 has the additive in it. The back should be a hair under 4quarts. And 2 quarts should work up front according to this:
https://www.ford-trucks.com/forums/9...ur-trucks.html
Note that those capacities are in pints, not quarts.

 

How come you would run dyno in the front? Cheaper?