Transmission Swap


Steel Soldiers Supporter
Culpeper, Va.
Guys, I went through about 25 pages here and can't find my answer. Simply, what is the best (or close to it) drop-in syncro transmission swap for the M37 driveline?

Thank you.


Active member
Steel Soldiers Supporter
santa cruz,ca
I remember my M37 as having a synchronized gearbox. They were supposed to from 1951 onward.
I just used my M37 as shipped and actually didn't mind the gerabox at all so no first-hand knowledge of swaps. Here are some things I found though...
The M37B1 transmission is liked better than the original M37 gearbox. The G741 Forum might be the place to check for details and easy swaps. I gather there are various gotchas about brake pedal locations and the like so your options might be pretty limited if you want something close to drop-in.

I think what you want is here, identification and listings for both the early and late NP gearboxes as used in the M37 and similar:

If you want to keep it as Mopar as possible, I'd check into various New Process gearboxes, I think both the NP420 and NP435 would likely fit with some work and are pretty likely to just bolt-up on the bellhousing side at least. I know they came in a variety of splines and input shafts though. Not fully synchro'd but second and up is a good start. They were replaced with the fully-synchronized NP4530 and NP445.

Might be an answer for you over here using Ford gearboxes:

If you want to run a Chevy gearbox and don't mind spending some $

Good luck and let us know how it goes.


New member
Ontario, Canada
They are in my experience good transmissions, But having never broken one I can’t really advise you any issues with them. They share parts with the T98, despite being made by Acme so parts aren’t hard to come by. I believe the input shaft is different in that it accommodates a larger clutch disc than the US M37. Up here you can find them fairly easily, however the pto is quite rare, and it has a reverse cut gear in comparison to the US version.
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