I've searched on line, have the owners & Haynes manuals. There seems to be some conflicting info so I'm hoping to get clarification.


First off, I have a 1989, 4.9 4x4 F150 with T-18 manual. What I think I'd like to do is this:


Front/Rear Differentials & Transmission - Mobil 1 15/50 Full Synthetic
Transfer Case - Mercon


Will I be OK?

 

what does the owners manual say to run? thats what i would stick with. good idea running full synthetic though..

 

Yeah follow the manual.

My 94 F150 with 4x4 calls for 80w90 in the rear diff, 75w90 in the front (dana 44), and Mercon ATF is both the manual tranny and transfer case. Directly from the manual.

 

I've always just used ND30 in my Bronco. Never had any transmission issues with it.

 

Just in the tranny or everywhere?

 

Just the transmission. I'd imagine it would be fine in the Tcase too... I had to re-read your original post and I must apologize as I misunderstood your original intentions.

I'd definitely suggest you run the thicker gear lubes in the diffs. The tranny and tcase will be fine with either ATF(Mercon) or low weight motor oil

 

Same with me.