What fluid do I use in an '85 NP833 MY6 tranny.

[LMN8UR]

I'm getting ready to convert my '72 to a three speed overdrive. Somewhere I read that this tranny (Supposedly out of an '85 truck) used automatic fluid. Now I'm confussed.

Hoping to do the convertion tomorrow, any advice?

[Longhorn Man]

I'm moving this to the 73 - 87 group... I'm sure they'd know.

[Green Machine]

I've had a couple of these trannys, one had Dexron and the the other had regular gear lube. I think Dexron was the original fluid.

Dexron seems to thin for me, and dino 75-90 too thick when cold. Synthetic 75-90 GL5 too slippery for synchros.

So the best lube IMHO would be Redline Manual Trans fluid. Thicker than dexron, buts flows well cold, and has less friction modifiers (slippery stuff) in it so the synchos can do their job.