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The Unicorn; Or M37 broken long side axle shafts

jollyroger

Member
647
5
18
Location
Centennial, Colorado
I am starting this thread to give some knowledge to the people that may not have much experinece with the M37. And some substantiation to the debate about how strong M37 axle shafts are. This subject has been debated at length on this forum. However ..........nopics
 

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jollyroger

Member
647
5
18
Location
Centennial, Colorado
To give everyone some background info about what happened I will explain.

Dad traded for the truck in the picture. It's missing a bunch of sheet metal. It's on crappy, old, worn out tires. It has a 327 Chevy with a 2 bbl carb. Nothing special in the engine. SM 420 trans.

I was at the top of our driveway out by the highway. It's concrete and falls off with a 6% grade for 440 feet. I was backed up to the gate, let out the clutch, let it get rolling and got on it. Bang! Brummmm, Brummmmm! I went about 30 feet and the truck just went limp. I knew what happened right away. Got it back down the driveway to the shop in front wheel drive. I pulled it apart. Both rear axles were new and so was the center section. When I say new I mean new, or new old stock. But definitely not substandard or old been run forever parts.

So in less than 6 hours with the truck, lighter because of the lack of sheet metal and parts, low power 327 V8, crappy old worn out not sticky tires, and brand new parts in the rear end it broke the long side rear axle shaft.

I hope this pretty much sums up the debate about the strength and service life of M37 axle shafts........They break.......The End.
 

scrapdaddy

Member
Steel Soldiers Supporter
409
11
18
Location
Dittmer, Mo.
Are you going to use Foote axles to replace or do you have some other new shaft. I always beleived the reasoning behind the breakage, was the metal is old school, not to todays standards. Right or wrong?
 

scrapdaddy

Member
Steel Soldiers Supporter
409
11
18
Location
Dittmer, Mo.
I've been lucky so far with mine. I'm running 11r16's Mich. and havn't snapped one yet. But I drive like an old man, Wait a minute, I am an old man!
 

Gamagoat1

Active member
744
43
28
Location
Kiowa, Colorado
It sure doesn't take a V8 to break em, new or old. I broke two long rears, with the six, four wheeling on Mosquito Pass at about 13,000 feet. Pulled out the broken end and scraps and put in the trail ready spare, and almost immediatly broke that one. Thank Dodge for the front wheel drive that was still working.
 

jollyroger

Member
647
5
18
Location
Centennial, Colorado
Are you going to use Foote axles to replace or do you have some other new shaft. I always beleived the reasoning behind the breakage, was the metal is old school, not to todays standards. Right or wrong?
I would have to agree with your assesment about the old school metalurgy. And design has a big role to play in this as well.

It's like the difference between Cast iron and Ductile iron. Ductile Iron has more Nickel cast into the mix and that hardens the metal making it more durable. Ductile iron was used more widely for cast parts like blocks, heads and rear end center sections late 60's to today. Ductile Iron can easily be mig welded using stainless wire because of the high Nickel content of the stainless wire.

The M37 axle shafts are made of cast steel. I have not seen the exact specs of the steel but I have heard it is a low grade steel. I have tried to research the exact steel used and my search has garnered vague results.

The splines on the shafts are a coarse 16 spline. And the splines are bigger in diameter than the shafts. So the shafts neck down just after the splines. this is not uncommon for axle shafts but the taper is not machined. It's cast into the axle. Modern axles have fine splines and more of them. Most axles in that size have 27-32 splines. And they are more refined with regard to the casting material, process, hardening and machining done.

I will be replacing the axle shaft with one out of another axle. But I'm interested in some aftermarket shafts so they can hold up behind this "powerhouse" 327 in the truck. rofl
 

jollyroger

Member
647
5
18
Location
Centennial, Colorado
The axles were always a problem from what I've been told/read.
HOWEVER...

I would think that romping on that 327 was a bit more power than that poor ole 230 6 banger would have applied??:D2cents2cents
You are absolutely correct. The 327 no matter how badly tuned will put out more power and torque than the 230 Derge flathead........It was amazing how quickly the shaft grenaded......I did not even get a chance to shift gears. :grin:
 

98taco3

Member
390
4
18
Location
Berthoud, Colorado
what about getting the original axles cryo treated? Bobby long (toyota truck axle guy) developed some sort of process to treat axle shafts. His products have a great reputation and he will treat other make shafts too. His company is named longfield and might be worth a shot!
 

trucknut

Member
46
2
8
Location
winnipeg, manitoba
Hi Jollyroger
Years ago I read that a company made hd axles for the m37. I think this is the company mentioned- Bobby Henry Machine Works, Running Springs CAlifornia. Phone 909-867-4656 .2cents
 

Capt.Marion

Active member
1,811
15
38
Location
Atlanta, GA
You don't have to work too hard with the 230 to do in an axle shaft, either... especially if you do the mods to allow you to have Low Range without engaging the front axle.
 

Oldfart

Active member
1,063
26
38
Location
Centennial,CO
It sure doesn't take a V8 to break em, new or old. I broke two long rears, with the six, four wheeling on Mosquito Pass at about 13,000 feet. Pulled out the broken end and scraps and put in the trail ready spare, and almost immediatly broke that one. Thank Dodge for the front wheel drive that was still working.

I too have limped home in front wheel drive (more than once). That was the reason I started collecting M37 parts trucks. I just needed a source of axles. If you collect enough parts trucks, you notice mostly what's missing are long side rear axles.
 

JasonS

Well-known member
1,635
113
63
Location
Eastern SD
IIt's like the difference between Cast iron and Ductile iron. Ductile Iron has more Nickel cast into the mix and that hardens the metal making it more durable. Ductile iron was used more widely for cast parts like blocks, heads and rear end center sections late 60's to today. Ductile Iron can easily be mig welded using stainless wire because of the high Nickel content of the stainless wire.QUOTE]

Ductile (nodular) iron differes from gray cast iron in that the graphite is in nodular form instead of flakes; generally by the addition of magnesium. I don't believe that nickel plays any part.
 

jollyroger

Member
647
5
18
Location
Centennial, Colorado
From Wikipedia:


A typical chemical analysis of this material:
Other elements such as copper or tin may be added to increase tensile and yield strength while simultaneously reducing elongation. Improved corrosion resistance can be achieved by replacing 15% to 30% of the iron in the alloy with varying amounts of nickel, copper, or chromium.

Please note the last sentence.

From Wikipedia:

Ductile iron is specifically useful in many automotive components, where strength needs surpass that of aluminum but do not necessarily require steel. Other major industrial applications include off-highway diesel trucks, class 8 trucks, agricultural tractors, and oil well pumps.




According to my Modern welding Handbook: "This Ductile Iron can also be obtained alloyed with silicon (3-6 percent) if heat resistant properties are desired, or with nickel (8-35 percent) and chromium (5 percent), if corrosion resistance is desired, plus heat resistance." "Ductile Iron has been satisfactorily welded by arc welding using a 60 percent nickel, 40 percent iron electrode."

Here's the information I have been running with over the years about "High nickel" Ductile Iron: Q: What is a Bowtie, or heavy duty (nickle) block and do I have one?

[SIZE=+2]A:[/SIZE] Tin and nickel are two metals that are commonly alloyed with cast iron to improve durability, hardness and heat dissipation. Some production engine blocks have the numbers "010", "020" or both cast into their front face, just above the main bearing bore. (The timing cover must be removed for these numbers to be visible.) If both numbers are present, one about the other, it indicates that the block alloy contains 10% tin and 20% nickel. A single number, either a "010" or "020" represents the amount of nickel and indicates negligible amounts of tin. No numbers, other than the casting numbers that are typically found beneath the timing cover, translates to only minor amounts of tin and nickel being present in the block alloy. However, cylinder wall thickness is the overridering consideration - and a block with no tin or nickel and thick cylinder walls is generally preferable to a high nickel block with thin walls.



I am sure everyone can find any answer they want on the internet.............After reseraching this heavily I would have to say we are both right. The term ductile iron has more to do with the microstructure and process of the iron. Nickel is cast into the iron for seemingly several purposes.:beer:
 
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jollyroger

Member
647
5
18
Location
Centennial, Colorado
Back on track I want to thank all you guys for the tips on where to get aftermarket axles. I had a line on some several years ago and that dried up. I'm gonna call Foote today and ask some questions about the manufacturing process, material and cost. When I have results I will let you all know. I'm also going to follow up with the other links as shared by other SS members. That's why I posted what I did here. So we all could get a discussion going about how to fix one of my ultimate frustrations with the M37.

Thanks guys.:beer:
 

jmassenga

Member
58
0
6
Location
AK
Also not hard with a locker that breaks and turns into a spool; 2 longs and a short went before I figured out the real source of the problem. There is no doubt that they are the equivalent of a fusible link in the drivetrain!
 

IGALL1

New member
6
1
0
Location
Iota/LA
I have a 1960 M37 that I bought when I was 16. I drove the @@@t out of it on my crawfish farm every day for years. Climb levees, running over trees, mudding, pulling fallen trees, uprooting trees, pulling trucks out of the mud, fording, crawling over things that shouldn't be crawled over and every other type of abuse you can think of..... That thing was famous in high school! It is bone stock and I love it. One day I was jerking chicken trees an willow trees out of the ground for fun and I got over confident... I hooked up to a hackberry tree about 20" in diameter and popped clutch! Hit it three times and it didn't budge. My buddy was with me egging me on so I backed all the way up to the tree and caught 2nd gear before the chain tightened. We both got whiplashed into the windshield and my buddy's head spider webbed the passenger windshield pane. At the same time I heard a loud PING come from the rear end. I unhooked, drove to the road pulled it into 2wd high and stomped it....and started rolling backward! I limped it in 4 low to the shop and soon realized the long rear axle was shattered! I pulled out 4 pieces and couldn't get the final stub out because it was jammed in the chunk. I also could't get the chunk out because the stub was locking it in. Here is the tip I figured out: I got my stick welder and found a piece of 1" flatbar and used the last inch of about ten welding rods to weld the flatbar deep inside the tube to the stub. I then welded another piece of flatbar to the end of the piece sticking out of the tube at a right angle. Then I hammered the broken piece out! It worked great!
So it took slot of torture to break mine. Maybe the metallurgy is inconsistent? Who knows. Good information on aftermarket replacements!
 
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