Tranny vent

[Kenneth Cole]

Hi
Does the M37 tranny have any vent?
Thanks
Ken

[John Waak]

Ken, since you don't have a reply from someone who knows the NP 420, I will venture a guess based on an earlier model transmission. The answer is yes, the transmission vents through the shift tower.

[Kaiser2boy]

Hmm, maybe thats why the cab in any M37 I have ever been in smell the same. Hot oil , canvas, OD paint.

[John Waak]

Indeed, it answers our publisher/editor/webmaster's question:

Why is it that the inside of old truck cabs smell so good?

[Kenneth Cole]

John
Thanks for getting back to me.
Is there an actual vent hole?
Thanks
Ken

[John Waak]

Ken, again, I am referring to the "After-Type" transmission which preceded the NP 420. On the "After-Type" there is a small slot in the base (or ball) of the shift lever. The slot measures 1/16 x 5/16 at the top of the shift lever ball. A rubber shift lever boot keeps dirt from falling into the transmission, at least in theory if not practice. Whether the slot I am referring too is an actual vent or serves another purpose I am not entirely sure. It does, however, provide at least one place by which pressure can be equalized.

On the NP420, Lift the shift lever boot, and look for a small opening. Unless gunked up with dirt, I would conjecture you will find it.

Good luck.

[Kenneth Cole]

Thanks John, will do.
Ken

[Charles Talbert]

Not a vent at the shift tower

Actually and literally there is no established vent, however there are numerous ones. There is no pilot shaft oil seal, so it is wide open.

The slot in the shift lever ball is to hold the lever in alignment. Have you ever noticed how far the shift lever travels toward the passenger side when trying to shift into reverse on a worn transmission? That is because of excessive wear in the slot and the pin it rides on. Yes it certainly can be a vent, but no it was not intended as such. The reason why the later NP420 is much less prone to have this excessive travel is because it has a slot in both sides of the ball and a pin that rides in both. Maintains alignment much better with a way slower rate of wear.