The hubs can't take the power, have you seen them? They are way overbuilt.
Now, the Cv's are a different matter. If your friend used the 8K or 10K cv's they will definitely break with some mild modes. Heck, they will break with a stock engine and some crazy off roading.
The 12K ones, they are a different beast all together. The joints and shafts are as big as the ones used in the Chevy 1 ton. The input shaft was increased a 1/4 inch, and they went from a 28 spline, to a 32 spline. Only way to break one of these shafts is to do the kind of rock crawling where you put your foot in it and don't take it off till you reach the top, or something breaks. Usually the shafts will.
I would be more worried about the differential, as it can only take 2,000 ft lbs continuously.

And you are right, the HMMWV does need a body lift to properly clear the Cummins.

 

No, I've never seen them, I just work on his truck. I've seen them inside and out, I've held the broken pieces from the hub internals when we changed them out at his garage where it was trailered to. Granted, the half shafts break more often than the hubs but no, not even the 12k's are overbuilt for a turned up cummins.

The rear diff has had the gears replaced once but has held up well so far. This thing has seen A LOT of Jeep trails both here in CA and over in NV, it does pretty good for a widebody!

 

hey BioHMMWV, you should do a write up on how you did your np 205 backwards conversion. thats something id be interested in doing but a little confused as to how to make it work. did you have to offset the rear end to allow for the driveshaft when the transfer case is offset backwards? and does it only work all the time or can you shift it on or off?

 

Wow is all Ive got to say about that.

 

I find that hard to believe, but, if you say so. What exactly broke on them? I know some of the hubs had a lower spindle that was defective, and the spindle would shear right where the outer bearing is located. The default was blamed on a machining defect.

There is not much to it. The rear diff does not have to be offset. Just use a divorced 205, and where the original input was, make that into the output for the rear. Where the original output to the rear was make that into the new input. The original front output is not used as it will now be facing the rear. I can take pictures when the weather clears up if you like.

 

ya thatd be great. thats an interesting design. does it always have to be on or can you still put it into normal mode? or would the driveshaft not spin unless its engaged?

 

There's a company out of Georgia, called Diesel Depot, that has turned out a couple of H1 4bt diesel swaps. There are some Youtube videos of different 4bt swapped Hummers.