FGZ

Redline's MT-90 was one of the only GL-4 gear oils I could find that met the 75W-90, which I need due to a cold climate. So it looks like I'm switching to synthetic (MT-90 is) in the trans and t-case in my '85 4Runner.

Some folks suggest a mild flush, Amsoil makes one, if you're switching dino to synthetic in the motor. Anyone know whether something similar is needed for my transmission?

scuba

No. Just drain and fill.

FGZ

Forgot to mention this is a 5-speed.

Thanks Scuba.

I just drained it, and got some light-colored foamy looking stuff at the end like you'd get with water mixing in. Hopefully that's from an old problem and I don't actually have water coming in from somewhere. But now I really want to flush it before I put pricey Redline in. I may mix and match ~3 qts of what I have laying around so I can get some sort of lube through and wash out the nastiness. For the "wash" I'll let the truck idle in 2nd gear with the t-case in neutral while my concoction is in there. After about 10 minutes things will be warmer so the fluid will run easier when I drain it again, and it should bring more contaminants with it at the same time.

THEN I'm refilling with Redline and hoping for the best.

millball

diesel fuel would be a good flushing solvent