I'm changing the fluids in a 1995 F-250 I recently purchased and suctioned out the front differential- appears to be a somewhat lightweight gear oil. The manual gives a specification for the front differential but I can't figure out what it's supposed to be? 75W-90? The rear appears it should be 80/90 but I'm considering using synthetic would 75W-140 be OK in the rear? Thanks in advance.

 

if you dont get a response by monday, ill look it up on mitchell/alldata when i get back to school

 

The recommended lube is for both normal and severe in front 75W-90 and for normal 80W-90 and severe 75W-90 in the rear.
Why would you not want to use the recommended fluid?

 

Thanks- my manual doesn't actually specify which weight fluid to use in the front, it states to use "4X4 Gear Oil" and gives a Ford specifications number. A Google search and search of this site for that number (WSL-M2C191-A) didn't give me much (if any) more info on the weight of the oil to be used. The rear is specified as 80W-90. I ended up changing the front with semi-synthetic 75W-90. I decided not to change the rear, as it was topped off and the lube appeared very clean and light in color making me think the previous owner changed it recently.