A buddy of mine says he will change the trans fluid and diff fluid at his mechanics school for me. I was wondering whats a good fluid to use. i looked in the book and it said to use SAE 85W/90 gear oil for the trans and hypoid gear lubricant SAE 80 or 90 for the diff. By the way the rear is a 3.55. Should i just get stay with the stuff in the book or is there anything better.

1987 F150 4.9L, 4 spd manual 2wd
31x10.5x15 BFs, 3" suspension lift
167,000 and counting

 

 

I'm just trying to make sure I have this straight, you have a manual trans. yes..! Anyway I switched all my fluids to synthetic for this reason. The molecular shape of natural fluids is small rods and cones, while the molecular structure of synthetics is small ball bearings. This is infact very very small differences, but the way I look at it is this so are the clearences in your engine and trans. The molecules of the synthetic are smaller so they will find anything wrong with your seals. It doesn't cause your seals to leak but it will show you any leak that you may have. This is just my opinion take it for what it is worth. Besides I like the extra protection it gives, small but to me it makes sense.

cpnhgnjnky
95 F150 Eddie Bauer 4x4 5.8L
A whole bunch of stuff