93 dodge 3/4 ton axles.

[gravely8199]

Input needed here. I found a 93 cummins pickup and need advice from anyone who knows anything about axles. from what I have found they are 67.5" between wms but I cant find the dim on the m37 axles. Anyone know it? Any advice from those that have done a swap? They are 3:73 gears which are a bit steep for 37" humvee take offs but this would put 65mph right around 2100 rpm if I didnt screw up my calculations too bad. The peak for the cummins I want to install. I have a 4bt lined up to go in with a 4sp but I believe the 5sp in the truck should work with it too. Friends are telling me to use the 6bt but that is a bit heavy at around 900 lbs for only 160 hp. But I do like the 400lb/ft tq rating!
And yes,I would be willing to build a dog house if it would pay off.

Lets hear it from all sides folks!

[Cal_Gary]

I'd PM Charles (m-series rebuild) as the info you seek is within his line of business, dealing with the Cummins swap. He likely has the expertise you need.
Gary

[tbone1004]

WMS to WMS doesn't really matter in an axle swap, track width matters. The backspacing between the HMMWV rims and the M37 rims are going to be different. M37 has a track width of 62" I believe. The HMMWV stock rims I believe have 7" of backspacing, so you need a WMS to WMS in the 65-66 inch range assuming you want to use same width tires, the HMMWV tires are obviously much wider, so at a width of 12.5 instead of 9 you need to go out 1.75 on your track width for steering clearances making total width addition about 3.5 inches on each side. 67.5" WMS to WMS puts you right where you need to be to maintain the same clearances for steering linkages and what not. You're also going to obviously have to change the whole steering system over from push-pull to crossover with those new axles.

Gear ratios in the axles depend on how wide the transmission gears are. If you're using gear ratios like what is in the stock Tcase, standard for the NP435's and comparable to all of the granny gear 4spds, you're going to hate it and have a lot of problems getting up to speed because the Cummins don't have a wide rpm band. You need something like a close ratio ZF5 out of a Ford or the NV4500 to be able to actually get up to speed. The takeoff rims are also VERY heavy with the big tires so you're going to have to get them rolling. I think you'd be far better off finding axles with at least the 4.10's, if not the 4.56's from the CUCV's.

6bt is going to be better balanced but is also going to require a complete redesign of your suspension system to handle the weight. If you're wanting to go that route there is a build thread where a guy is putting the 6bt on top of a mid 90's Dodge with the 6bt. That would save a lot of problems and engineering on your end, as well as a boat load of money in building brackets.

[adamkw12]

I did this same swap about a year and a half ago. I took a dana 60 front with dually hubs and a dana 70 with 4.56 gearing for my axle swap. The front axle I shortened 3.75" on the long side so the spring perches lined up and so there was equal spacing on both sides. The dana 70 I had to use 1.5" spacers since the dually rearend is narrower than the srw rearend. The reason I kept the dually hubs on the front was the H1 wheels will not clear the tie rod ends without special mounting brackets. I don't remember the exact measurement but I believe I am about 2" or 3" wider, because of the wider tires and the dually hubs. I have not really road tested it yet, but we will see how it drives at higher speeds. When I drove it with the 4.56 gears, nv4500 trans and 37" tires it was pretty high geared. I think some of the problem was I didn't have any weight to the vehicle so it really scooted down the road. I just put the bed and all the other sheet metal on, so we will see if adding that weight changed the handling. I wouldn't use the 3.73 gears and would opt for at least 4.56 gears. On the motor, if it was me, I would use the 4bt with a 5 speed. The 6bt only fits with a lot of modifications and it is more motor than you really need. My stock 360 is more than enough power for mine and since you're probably not towing with it, it is wasted power for these trucks.

[gravely8199]

dually axles,huh? didn't even think of that. i know of a set of d60 d80 from a 97 i could get measurement on . thyve got 4.10s and im planning on the dually centers welded into H1 rims any way.