Chevy SM420 or NP 435?

[oldestof11]

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

[Fnschlaud4620]

What are you trying to build?

Are you planing on putting your cummins in the suburban?

Do you plan on keeping it 2wd?

That cummins will scream with out an overdrive trans, if your suburban has a low ratio rear end in it.

both the sm420 or the np 435 will take alot of abuse. but you will need the chevy breadtruck bell housing with a flywheel. IF you can find one, they go for 500-600 $. You still need a good clutch and I believe the biggest you can go is a 12".

[MMiller]

They work perfectly fine behind a gasser with a wide rpm range to work with, and can't effectively use a OD. Everyone I've talked to that has used one behind a Cummins hates the large gear spread, and way to many rpms when running around empty.

You've also got to remember the NP435 used a smaller input shaft and output shaft then any manual dodge ever used behind the cummins. I'm sure there is a reason or two behind that.

FWIW I've used both and watched both take tons of abuse from Big Block Chevies and Big Block Mopars, but I'd never think about backing up my cummins with one. A getrag or nv4500 will be great, and if doing alot of heavy towing then a 6 speed.

Michael