Non-synchro tranny vs NP 420

[maineSS]

I'm going to temporarily swap in a 1958 NP 420 into my '49 PW while I see what ails the crashbox. Is the shaft dia & spline count of the 420 different than the "Up To" (early series) tranny? It would be nice to know before finding out they're different in the middle of the swap.

[Gordon Maney]

Can you answer that question with a clutch disc part number comparison?

[Frank Irons]

I'm going to temporarily swap in a 1958 NP 420 into my '49 PW while I see what ails the crashbox. Is the shaft dia & spline count of the 420 different than the "Up To" (early series) tranny? It would be nice to know before finding out they're different in the middle of the swap.

What vehicle is the 58 NP out of? If it is out of another Power Wagon you will need to use the bellhousing from the '58, the transmission bolt pattern is different than the earlier trans.

Frank

[maineSS]

I'm hearing that the m37 trans will bolt up to the earlier bellhousing, otherwise you have to go with the 56 and up. Also, righthand floorplate and tranny hump, possibly clutch and PP, as 11" clutches take the 1 3/8"/ 10 spline input shaft vs the earlier 1"/10 spline input shaft. Also heard the 420 top can fit the m37 box, still checking this one out.

[CSCameron]

So, was there only one tranny used in the M37? What was its designation? Are the M37 trannies full synchro or just 3 & 4th gears?

Thanks! I have a 55 with a crashbox and I also have a '64 synchro tranny that I was thinking of swapping in, but this has me interested. Seems like it would be a whole lot easier to just purchase and swap in an M37 tranny?

[Frank Irons]

I'm hearing that the m37 trans will bolt up to the earlier bellhousing, otherwise you have to go with the 56 and up. Also, righthand floorplate and tranny hump, possibly clutch and PP, as 11" clutches take the 1 3/8"/ 10 spline input shaft vs the earlier 1"/10 spline input shaft. Also heard the 420 top can fit the m37 box, still checking this one out.

Both the early M37 and later M37B transmission will bolt up to the early PW bellhousing. Shift tower is farther forward than the non syncro transmission. I did this swap on my WDX. The later M37B trans is the better of the two.

Frank

[maineSS]

The reason I'd like to use the 420 shifter plate top is the peculiar shift lever the M37 has. Also, I hear you need a different brake pedal with the 420 tranny, so a 420 switch into a non-synchro truck is rather involved, especially if you're only looking for a temporary installation. I believe only 2nd to 3rd, and 3rd to 4th are the only gears synchronized in the M trannies.

[Frank Irons]

I had to grind a little off the brake pedal to clear the PTO but was able to use the original pedal. I am not sure on the top covers interchanging but the early M37 trans has an entirely different shift fork arrangement. You are right on the synchronizers.

Frank

[maineSS]

I've heard the quick way to recognize the early M-37 tranny from the later M-37 B1 is the type of shift lever- the early one has a 2-piece clamp-on construction, whereas the B1 tranny is one-piece going into the shift tower. None of the parts interchange between the two transmissions. The PTO's use different idler gear part numbers, and these gears are supposed to be changed for the correct one when swapping early PTO's onto late trannies, and vice-versa. However, people have supposedly ignored this with no apparent problems- but since I have no personal experience with this, I'm not going to recommend it. Keep in mind the Canadian-built M's used the 251, so their trannies won't bolt up to the 230.

[Frank Irons]

I believe the clamp type shifter is also on the later M37 trans. The easy way to tell the difference besides the casting date, is that the shift tower on the later transmission has two pins to retain the spring retainer in the cover. The Canadian M37 uses an Acme transmission, a completely different trans. I have also heard that the pto is the same but have no experience there. These topics have been discussed many times on the G741 Forum, do a search on there for more info.

Frank

[Natejohnson17]

I believe the clamp type shifter is also on the later M37 trans. The easy way to tell the difference besides the casting date, is that the shift tower on the later transmission has two pins to retain the spring retainer in the cover. The Canadian M37 uses an Acme transmission, a completely different trans. I have also heard that the pto is the same but have no experience there. These topics have been discussed many times on the G741 Forum, do a search on there for more info.

Frank

Hello Frank, I don’t believe I have permission to PM yet. I picked up a NP420 to install into my 48’ Power Wagon. Could you tell me what additional parts I am going to need besides the transmission hump/tunnel? Thanks for your help!!

[Matthew Welcher PWA]

Hello Frank, I don’t believe I have permission to PM yet. I picked up a NP420 to install into my 48’ Power Wagon. Could you tell me what additional parts I am going to need besides the transmission hump/tunnel? Thanks for your help!!

Nate, We can refresh this topic, let us start from the beginning. You are wanting to put the NP420 into your Power Wagon is that correct? And your Power Wagon is an early with the first series transmission?

[Natejohnson17]

Right. I have a NP420 out of a M37B1 to install. My 48’ has the early crash box in it now.