I found a source of these trannys and was wondering if either of them would be a good tranny behind a cummins. They seem cheap enough ($500 for either one) without a clutch or flywheel. How about bell housing adapters, flywheels, and clutches? I found a website that out of the top 5 off road, they came in 1st and 2nd, respectively. The NV4500 made it to #5

Thanks!

Jon

 

Depends what you are doing with it. The 420 is an archaic design but stout. The jeep guys like it because it is very compact and has the 6.something first gear ratio. They started using them in the 40's....old tech. The 435's are a great 4spd used in dodges and fords. I have one mated to a 205 sittin in the drive and just from looking at it you can tell how stout it is. Its hard to get "hard" parts for the 420 and I do not thing it would do well behind a cummins, the sm465 that replaced it would do well, I put one in a jeep I had and it really shifted like a truck, but none of these mentioned have an overdrive. The 435 would probably work fine with the cummins...

 

These are both fairly rugged v-8 gas tranny's. I am not sure how well they would wold up the the massive low end torque of a Cummins. The Chevy's have a 1-1/8" input most always a 10 spline. Ford uses a 1-1/16 10 spline on the NP 435. They would probably live in a light pickup with a stock 5.9 that was driven nicely. Drop the clutch and I'm sure the input would snap like a twig.

As far as bellhousings, I am not sure. Maybe you could get the cummins to chevy adapter and a chevy trans and bell. Maybe there is a big block mopar bell for the NP 435 that would bolt to a diesel. I have heard that some guys replace the getrag with a 4 speed. Dodge used a lot of 435's.

The SM420 is the original "granny low" four speed, first gear is like 7:1. Rockcrawlers like these.

 

I was typing the same time as you Mike! I must be slower.

 

What vehicle are you trying to put this in?

 

I would trust an SM465, the 4 speed which replaced the SM420 in fullsize GM pickups sometime around 1970 and was available until the early 90s. The 465 was also used in small trucks and is very durable in that application. The 350, 366, 427 and 8.2 Detroit are powerful (OK, the 427 anyway!), but not torquey engines, but 30K ++++ loads are respectable and it takes a good transmission to handle them! I am not sure if GM offered the transmission behind any larger diesel engines.

Also, the transmission was used behind the 3.9 Cummins in box van apps. This would be a good source for for the parts that you need.

 

This is going into a 1987 2wd Suburban, my friends I am looking for a cheap tranny so I could get it started then get a Getrag or NV4500 when the money comes along.

Jon

 

Cool! It would be a great transmission for that. You could probably find an sm465 for next to nothing and ebay has the adaptors and such from time to time.

 

It will be cheaper just to use the Getrag or NV4500 the first time around. You will be spending at least $500 - 750 for the parts you will need. Add that to the price of the transmission + driveshaft modification cost & you still end up with a non overdrive transmission. Adapting any Cummins engine to a Chevy driveline generally costs more than any other method when ever you start buying individual parts.