80w90 and 85w140 why?

[njkev7]

Why does the front diff take 80w90 and the rear take 85W140. Why not 85w140 for both?

 

[gijoecam]

Ford has changed their recommended lubricant for the front axle several times. No idea why. I'm almost convinced you could run canola oil in the front diff and it would be fine in a pinch.

Best guess? Different operating conditions, loads, bearings, volumes of fluid, etc. call for two different fluid requirements, and one did not meet the spec at the time.

 

[IZwack]

I think its because of the different manufacturers. The front axle is under Dana specifications, not Ford's.