Changing the fluid and wheel seal and I am getting conflicting info.....

My owners manuel and Haynes (I don't have alot of faith in Haynes) both say to use 75-140 synthetic oil. But the tag on the axle says 75-90. What's up with that and which way do you think I should go, is there a good or bad to using the 75-140?

03 scab
4.2
2wd
8.8 open diff
209k miles


Thanks in advance
Jim

 

As long as you add friction modifier you are good.

 

It's an open diff, so no modifier needed the way I understand things.

My question was more about the viscosity, 75-90 vs. 75-140.

Thanks

 

Ortiginally it was supposed to be 75w90. Ford changed the specs some years ago to 75w140 for all rear diffs.

 

Kingfish got it.

 

Got it, Thanks Guys!