Hey, i was just wondering what viscosity manual trans oil that i should use in my truck. I'm not changing the fluid or anything, im just adding some more to top it off.

 

Mercon ATF is what ya use. Takes about four quarts from empty, so might as well drain and start with all fresh fluid.

Adrianspeeder

 

a 5sp in a '90 takes atf? doesnt sound quite right to me..... you might want to give the auto zone a ring; I'm guessing 80w 90

 

I thought the same thing.. i've never heard of putting atf in a 5-speed manual before. I remember reading in a repair manual a while ago that it took something like 70w 90w or something like that but i wasnt quite sure...

 

Nope the mazda M5OD-R2 used from 1988 till current uses ATF. Along with both versions of the ZF5's and the ZF6. Your older T-18/19 and NP435s used the heavy gear oil.

https://www.f150online.com/forums/sh...d.php?t=211867

Adrianspeeder