A little research from ya'll.

[Alxj64]

QUESTION!!!
I'm doing a little bit of research for some writing and analysis on these old trucks...

How many of you have broken an axle shaft, in what truck type, size tires ,and what were you doing when it happened? And were you stock powered or more power? V8 or Diesel?
Flogging it on Asphalt? Mud, Rocks, towing? Snow?

ANY info and Pictures would be greatly useful! Thanks in advance!

[MasterYota]

My first experience with Mill Spec. trucks was a 52 M37. If I dumped the clutch around 2000 rpm in first gear (high range) it felt like would lift a tire as it jumped off the line (Canadian version, 251ci. Flat head 6, 9.00:16 NDT tires). This was done only a few times on asphalt, with no breakage.

I also performed that stunt a few times after I repowered it with a 350 SM465 spd. combo, and again never broke or damaged anything (but it was a heck of a lot more fun to drive!!!) Never broke anything in the dirt or offroad either, probably due to the lack of traction provided by the NDT's...

My current 53 M37 appears to have a couple of stripped bolt holes (missing bolts) on the wheel hubs where the rear axles bolt on. I have yet to confirm if this is due to the bolts being sheared and then removed, or just overtightened by an inept previous owner.

My research (via the articles on this site and some general experience) has led me to belive that the stock (M37) axles will probably stand up to moderate V8 power and probably a 37" tire for moderate trail usage. Component lifespan would depend mostly on its driven. Street usage and gravel roads or camping could probably get away with anything up to 42's or so. I don't think the stock brakes would be very effective at stopping anything larger than that.

The stock axles fall somewhere between a Dana 44 and a Dana 60 for strength.

[maineSS]

From what I've heard, the shortside axles fail most often. Trying to pull something in reverse 4WD is a good way to fail a front axle.

[HWooldridge]

I know of two incidents; neither happened to me personally but both are reputable sources. One was a guy going down the road at 50 on dry asphalt, normal conditions and the short side broke. Said he never could figure out why other than plain old fatigue. Replaced it with another stock axle and never had another problem - he still owns the truck so far as I know.

Second incident was a truck I owned that formerly belonged to a volunteer fire dept. They put a 250 gal pumper unit on the truck and blew two pumpkins and two axles, one long and one short - all over the course of about 15 years. I was able to buy it and a parts truck for not much money. I removed the pumper rig because it was WAY too heavy for a 3/4 ton, replaced the broken parts and had no further problems.

They are tough vehicles but not unbreakable...

[Alxj64]

Thank you guys for all of your help so far. I am learning that these trucks, given the amount of abuse they have all seen in the past 60+ years are much tougher than Anything you could ever think of buying today.

Keep the breakage stories comming ya'll. I much appreciate it, and them more I can learn from everyone the more everyone learns about their own trucks and their friends trucks.

Thanks.

[MasterYota]

I'm currently in the planning stages of hanging a GM Dana 60 under the front of my M37. Its an HD unit with the 35 spline 1.5" axles and factory 4.56 gears. I've got two choices for the rear though; a matching D60 30 spline 1.31" shaft unit, or a GM Corporate 14 Bolt with 10.5" ring gear and 30 spline 1.5" shafts. The 14 bolt is quite abit stronger, but I would need to regear it, and I'd loose about 1.5" of ground clearance. I'm torn at this point about which to choose.

I had also considered leaving the stock diffs underneath until they failed, but I figured its probably easier to sell something that hasn't been flogged to death. And its easier to do suspension and engine swaps and add power steeriong when the axle isnt in the way.

With the repower to a Big Block engine and plans for 40" tires, the cost of upgrading the stock brakes and driveline didn't make much financial sense. I felt it was more economical to ease two newer, stronger, axles underneath it. Also, parts are cheaper and easier to come by. I feel the ring and pinions are probably very similar in strength, but the axle shaft strength is hands down superior in the 60. The newer metalurgy alone proves this.

[Bruce in BC]

Hmmmm

There are a few rear Dana 60 with 35 spline axles but finding one would be a problem . The 14 bolt is easier to set up than the dana 60 . I have a 14 bolt in my trash truck and a dana 70 in my carryall . Except for the fact that there are way more gear ratios for the dana 60 than the 14 bolt I think they end up about the same . The 14 bolt is cast iron some of the danas are nodular iron .

[MasterYota]

There are a few rear Dana 60 with 35 spline axles but finding one would be a problem . The 14 bolt is easier to set up than the dana 60 . I have a 14 bolt in my trash truck and a dana 70 in my carryall . Except for the fact that there are way more gear ratios for the dana 60 than the 14 bolt I think they end up about the same . The 14 bolt is cast iron some of the danas are nodular iron .

Those were basically my feelings as well. I know there are aftermarket upgrades to bring a rear D60 up to 1.5" shafts and 35 splines. I belive the 14 bolt is a stronger gear set just due to its physical size (10.5" vs. 9.75) and the addition of an extra pinion support bearing. The 14 is also easier to setup, as it doesn't use shims to align the gears. I've got 1 of each diff already, I'm just trying to figure out where best to spend the money.

[Steve G]

One older guy that I used to work with thought the power wagons were junk. He was working at a job site in the winter that was complete mud when warm and frozen when colder. On some of the warm days they left the power wagons in the mud at quitting time. In the morning the trucks would be frozen down in what used to be soft mud, he never said how deep. His complaint was that they kept breaking axles trying to drive the trucks out.

Sometimes it's not the truck's fault, just the operator's.

[MasterYota]

One older guy that I used to work with thought the power wagons were junk. He was working at a job site in the winter that was complete mud when warm and frozen when colder. On some of the warm days they left the power wagons in the mud at quitting time. In the morning the trucks would be frozen down in what used to be soft mud, he never said how deep. His complaint was that they kept breaking axles trying to drive the trucks out.

Sometimes it's not the truck's fault, just the operator's.

I've heard stories like that as well, particularly the front axles would fail if the tire was bound up (or frozen as in your case). I agree with you, its mostly operator error.

[Keith in CO]

D60/14bolt

I'm currently in the planning stages of hanging a GM Dana 60 under the front of my M37. Its an HD unit with the 35 spline 1.5" axles and factory 4.56 gears. I've got two choices for the rear though; a matching D60 30 spline 1.31" shaft unit, or a GM Corporate 14 Bolt with 10.5" ring gear and 30 spline 1.5" shafts. The 14 bolt is quite abit stronger, but I would need to regear it, and I'd loose about 1.5" of ground clearance. I'm torn at this point about which to choose.

When I measured the front frame width of my M37 relative to a D60, it looked like I would need outrigger front spring hangers to avoid custom shortening the long side. Is that your plan? Check this: http://www.ruffstuffspecialties.com/...c89468b73a62b8

I've been mulling over whether to go with a D70 or 14 bolt rear on a project, and at this point I am leaning towards the 14 bolt. I have both axles, and both would require gears, locker and disc brake swap, but the 14b wouldn't need a carrier to go to 4.88s. Also, there is better aftermarket support for the 14b and replacement parts are dirt cheap.

[MasterYota]

When I measured the front frame width of my M37 relative to a D60, it looked like I would need outrigger front spring hangers to avoid custom shortening the long side. Is that your plan? Check this: http://www.ruffstuffspecialties.com/...c89468b73a62b8

I've been mulling over whether to go with a D70 or 14 bolt rear on a project, and at this point I am leaning towards the 14 bolt. I have both axles, and both would require gears, locker and disc brake swap, but the 14b wouldn't need a carrier to go to 4.88s. Also, there is better aftermarket support for the 14b and replacement parts are dirt cheap.

An outrigger for the front suspension was my thought exactly. I think it can be done without compromising strength or the integrity of the frame. I've seen the link before, and I think they would be an excellent way to go over building a set. My concern is the shackle end of the spring. I don't really want to mount a shackle on the bottom of the frame (or at that level) as I think it will make the truck too tall. I've been trying to figure out how to use a "through the frame" sleeve design, like a stock Gm, that would provide minimal lift, but a wide enough shackle to meet the offset spring, and still clear the frame. Any thoughts?