Cummins swap transfer case technical question

[grampsbutler]

I have a 1984 Suburban with the 6.2 diesel, 6" lift and 37" tires. I love the truck, but I am planning out a swap because I've always wanted a cummins truck.

Progress to date: I have a 6.7l Cummins which I had rebuilt and is now running on an engine stand. I have a G56 6 speed transmission which I am currently in the middle of rebuilding.

Here is the dilemma. I would really like to keep the chevy axles, but to do so I need a passenger side drop transfer case to go behind the G56. The G56 output shaft is 29 spline, and as far as I can tell my options are limited in terms of finding one which will mate up. I believe that my best option would be to get a NP241 out of an 88-92 dodge truck, and then get a special 29 spline input shaft. (such as this: https://powerdrivendiesel.com/product/np241modified29spline/) Can anyone confirm whether the late 80s dodge transfer case will have the same bolt pattern as the 2010 G56? Has anyone on here successfully done this mating?

Any other pointers would be very helpful.

The only other option would be to swap out the front axle for one with a driver side diff, and then I could go with the NP271 which I know will bolt up. Obviously this would be the more expensive route, and I would rather leave the steering and brakes intact, but if anyone has good reasons to go this way, I am open to advice.

 

[Bextreme04]

Your original T-case was a 208, right?

ORD makes a shaft and spacer to convert the 29 spline output on the trans to a standard chevy 32 spline, so you could use any chevy passenger drop T-case that was originally behind a TH400 or 4L80

https://www.offroaddesign.com/29-spline-female-x-32-spline-male-spud-shaft.html

 

[grampsbutler]

Yes the chevy original is an NP208. Thanks for the link.....

Question: I thought the clocking on the dodge transmission tail housing was different to the Chevy transmission? Wouldn't I need an adapter plate?

 

[nvrenuf]

@grampsbutler Check this thread on ck5.com. This is a 91 crew cab with a 5.9, G56 and np205. Iirc, the NV271 was too big to fit inside the frame rails (no idea about an NV241HD).

1991 v3500 - forever truck

obijuank5 submitted a new Build: 1991 v3500 - forever truck I still cant get over it. I bought a 91 v3500. Going to build this truck to be simple, reliable, and comfortable enough to take the family anywhere from the state parks to the county fair. And look ****ing badass while I do it...

ck5.com

 

[grampsbutler]

Just to close the loop on this for others considering the same swap.

I went with the NP241 out of an 89 dodge. I found one at a bone yard for $350. I swapped the input shaft for a 29 spline input shaft and replaced all the seals and bearings. The swap was very easy, and it lines up perfectly. The only issue was that the flange on the transmission tail housing is slightly too think, so the studs on the TC are slightly too short. It mates up but there is not enough thread engagement. So I'm going with longer studs.

For anyone else considering which TC to go behind a g56. NP241 out of an 88-92 dodge is a straight forward swap, and it bolts right up and will give you the passenger side drop.

 

[Blazerbiker]

Since this whole swap has a lot of good info and a lot of the actual solutions, I thought I'd add an important detail. For this early type RH transfer case, the 29 spline input has to be the early type gear to match the gear pitch on the planetary set. There was a change in the planetary gears around '94 and while some report they can be mixed in certain situations, it's best not to mix them. So any RH 241 (GM or Dodge) will need the early gear pitch input to match. This limits the availability of the 29 spline input since they really only appeared behind manual transmissions in '94 trucks. But they are out there and that's what you need.