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Axle swap?
Has anyone performed an axle swap on a m37 that keeps the narrow track to be street legal? Im in the middle of rebuilding my M and i want to be able to easily lock it on both ends. Im afraid after doing alot of research that the stock axles just will not handle the strain. If anyone can provide some info i would greatly appreciate it. This could change the direction i go with my M. Also, i plan on running 38.5 x11 r16 TSL boggers on the stock rims to give you an idea of tire size. Thanks in advance.
I recommend a Dodge Dana 60 front and rear from a mid 70's doge W200/300. Rear will just about bolt in. Only requires a piece of steel tubing put around the bottom of the axle tube at the perches to take up the tube differences (M is 3.5" Dia, while the D60 is 3"). Dont let the sze fool you, the 60 is stronger. The front is more involved. you have to move the pad on the axle on the drivers side, and relocate the spring outboard of the frame on the passengers side. Bear in mind that even with tehse mods, the front axle is about 1/2" out of alignment to the passenger's side. This is because the D60 fromt spring pad is cast into the differential and cannot be moved, and, when the spring is relocated outboard of the frame, this is the minimum distance to move it. I have pictures of the swap in my rebuild threads in the general discussion portion of the forum. I've seen others use rockwells, but, as you pointed out, they need to be narrowed.
The D60s have several good points, like, being stronger, and cheaper, and better geared for more on road use (you can gear them down like stock M axles if you choose). They have much better brakes on them as well.
The other issue you will face is rear driveshaft angle. The T case will have to be unbolted from the crossmember and scooted all the way over to the drivers side, new holes drilled, and bolted back down. This is due to the offset rear output. Another option would be to refit a divorced NP205 from a 60's dodge W200/300. This case is gear drive like the original, fits well into the frame, and divorced. They can be had for a few hundred bucks, and are as strong, or stronger than the original case. Keep in mind, refitting this case requires new mounts. I have a few pictures in my rebuild thread of the rolled steel tube carrier I made for mine.
Im currently running a twin turbo big block, with the NP445 4 speed, and married NP203 full time case, with the D60s. I like the married setup, as it gives me a longer rear driveshaft, but, the floorpan needs to be modified to make it fit. If I were trying to do a married setup behind the stock engine, Id use an NP435 with a Dana 300 case. This is a very tough little geardrive case that would probably fit without need much, if any floorpan modification.
The D60s have several good points, like, being stronger, and cheaper, and better geared for more on road use (you can gear them down like stock M axles if you choose). They have much better brakes on them as well.
The other issue you will face is rear driveshaft angle. The T case will have to be unbolted from the crossmember and scooted all the way over to the drivers side, new holes drilled, and bolted back down. This is due to the offset rear output. Another option would be to refit a divorced NP205 from a 60's dodge W200/300. This case is gear drive like the original, fits well into the frame, and divorced. They can be had for a few hundred bucks, and are as strong, or stronger than the original case. Keep in mind, refitting this case requires new mounts. I have a few pictures in my rebuild thread of the rolled steel tube carrier I made for mine.
Im currently running a twin turbo big block, with the NP445 4 speed, and married NP203 full time case, with the D60s. I like the married setup, as it gives me a longer rear driveshaft, but, the floorpan needs to be modified to make it fit. If I were trying to do a married setup behind the stock engine, Id use an NP435 with a Dana 300 case. This is a very tough little geardrive case that would probably fit without need much, if any floorpan modification.
Actaully I'm in the middle of doing and axle swap on my truck. Like Josh said the axles from mid to late 70s w200 will work. But the front axle isn't a Dana 60 it is actually a Dana 44F. (Dana 44 Heavy Duty. Basically a Dana 44 gear set in a Dana 60 housing)
Here is a link to the web page where I'm keeping track of everything. http://www.leathernaturally.com/m37project.htm
When I measured everything up I found that from hub to hub the Dana 44f was actually shorter than the stock axle, the length being made up in the rims. Stock rims have a deeper backspace than say modern truck rims. In order to center the axle to the truck we had to move the passinger side spring out 1.5 inches.
Now I thought like Josh that the rear axle bolted right in, but it doesn't. Sorry Josh....here is what I've recently found. After I had gotten the truck sitting on the rear axle a few weeks later I noticed that the passinger side leaf spring was tilted about 10 degrees to the left. Upon further investigation I also saw that this was causing the leaf spring to deform. (Josh look at the pics of your truck after sandblasting you can see your spring doing the same thing). Also as Josh noted the rear diff is not centered in the truck....and yes if you keep the NP200 you will have to adjust it for the offset, an NP205 would be a better choice. When I lifted the truck off the axle the spring snapped back into it's proper position...and I mean it snapped back with a loud thongungungungung!
So I'm in the process of cutting the spring pearches and alighing the axle center under the truck with the diff centered in the middle of the truck. But due to time constrants and lack of cash flow, I haven't gotten around to finishing. I'm hoping to do some work this weekend or next and get it bolted in so I can get it to sanblasting and paint before the friggen snow flys!
Is it a bit of work, yes, but like Josh said in the long run it will be a better choice. Disk brakes up front, 4.10 gears (unless you go with a Dana 60 and GM 14 bolt from a CUCV which is 4.56 gears) and if you want for a lot less money than the disk brake kit for the M37 that is out there you can convert to disk in the rear also.
Here is a link to the web page where I'm keeping track of everything. http://www.leathernaturally.com/m37project.htm
When I measured everything up I found that from hub to hub the Dana 44f was actually shorter than the stock axle, the length being made up in the rims. Stock rims have a deeper backspace than say modern truck rims. In order to center the axle to the truck we had to move the passinger side spring out 1.5 inches.
Now I thought like Josh that the rear axle bolted right in, but it doesn't. Sorry Josh....here is what I've recently found. After I had gotten the truck sitting on the rear axle a few weeks later I noticed that the passinger side leaf spring was tilted about 10 degrees to the left. Upon further investigation I also saw that this was causing the leaf spring to deform. (Josh look at the pics of your truck after sandblasting you can see your spring doing the same thing). Also as Josh noted the rear diff is not centered in the truck....and yes if you keep the NP200 you will have to adjust it for the offset, an NP205 would be a better choice. When I lifted the truck off the axle the spring snapped back into it's proper position...and I mean it snapped back with a loud thongungungungung!
So I'm in the process of cutting the spring pearches and alighing the axle center under the truck with the diff centered in the middle of the truck. But due to time constrants and lack of cash flow, I haven't gotten around to finishing. I'm hoping to do some work this weekend or next and get it bolted in so I can get it to sanblasting and paint before the friggen snow flys!
Is it a bit of work, yes, but like Josh said in the long run it will be a better choice. Disk brakes up front, 4.10 gears (unless you go with a Dana 60 and GM 14 bolt from a CUCV which is 4.56 gears) and if you want for a lot less money than the disk brake kit for the M37 that is out there you can convert to disk in the rear also.
M37s are HMMWV in my world!
Wow...thats exactly what i was hoping to find was a direction to take at least. The swap sounds like a little work in the front, but i think it will be well worth it. How hard is it to find W200 axles though? I guess i need to start looking for a set. ill be keeping an eye on your build up as well. Thanks to both that responded.