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Well weekend tasks came to an abrupt end last night. I was doing a little landscaping work trying to remove a shrub root with FEL and felt a sudden lurch. i looked back and the right rear tire was not where it was supposed to be. I was in MFW drive low range. Discovered to my dismay that the rear right axle shaft had snapped just outside the differential seal. The tractor was purchased in 2014 and only has ~150 hours. Well maintained and garaged. I do use the FEL to its limit along with a pallet fork for lane gravel and firewood carry. I also bush-hog seasonally but no regular lawn mowing. I take good care of my equipment and tend to keep things for a long time. I am also fairly pragmatic about machines, things break and wear, and you fix what fails. But this kind of failure seems to me to indicate an overweight or over stress on the axle. That got me thinking maybe I was asking to much of this tractor. Rear tires are liquid filled and I do routinely carry a full complement of suitcase weights (8x42 lbs) on a Heavy Hitch on the rear three-point arms. Those rear weights make all the difference in stability and FEL safety. I would not think that ~350 lbs would cause undue stress on the rear axles but this kind of failure makes me wonder what happened. Is this rotational stress? What is the thinking here? What causes this kind of failure? Is this accumulated abuse or something acute?
 

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Whoa... that’s not good. That is some strange looking metal at the break.
 

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Can't like this...hate that this is one of your first post's.

I don't think the weight was the issue. Something else, weak steel, manufacturer defect...
 

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The two-tone coloring of that axle stub at the break would lead me to think that your axle was made from a defective steel casting. Never seen it on one of these forums before.
 

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Can't like this...hate that this is one of your first post's.

I don't think the weight was the issue. Something else, weak steel, manufacturer defect...
I have not asked too many questions on this forum because the community here is so great in sharing knowledge and opinions, I’ve soaked up a lot of stuff so thank you. However this axle thing took me by surprise. I am no metallurgist but I don’t like the looks of the break point.
 

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Yeah that looks like an inclusion of some type in the metal. I would assume the axle is drawn and heat treated. You will see the same thing sometimes in leaf springs they will snap right at a point where something dis-simalr is in the metal.

Ruff part is there are allot of places in the axle where it wouldn’t have made a difference but it fell probably very near the point of maximum strain.
 

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These things are made to drive around a job site with a backhoe on them...
Unless it was dropped from something high onto someplace hard it's gotta be an axle defect... I'll third the defect/inclusion theory...
 

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My first thought was how much weight was on the back and you answered that right away. I think that is less then JD recommends. Defect, I agree.
 

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Looks like a casting and outer ring is the heat treat.
Here is a better image. Will talk to Deere dealer tomorrow and see if we can figure out how to get this three-wheeler onto a roll back and in for service.
 

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Hate to see this, I'm no metal expert but that just doesn't look right .

Let us know what your dealer thinks. I would think his factory tech would like to see this also..

:dunno:
 

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I
Broke an axle on my simplicity legacy plowing snow just insidethe differential about 1” from the end. It was kind of an elongated twist break. Happens sometimes but yours looks like a defect break. My dad was a mechanic his whole life and showed me how they break. Not square like yours. The old torsion bars would break the same way
 

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Looks like a **** casting. The direct result of outsourcing and contract mfg with countries like China, Turkey, etc.

Very sorry for this unacceptable failure, best of luck getting it fixed up.
 

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Machining/ Tool & die background here...

It doesn't look like a casting to me. Doubt they use a casting for shaft material, bar stock is cheaper and easier to work with for shafts and heat treats better. Also more "standardized" with grades than castings.

That metal resembles a torsionally stressed (maybe a little bit of shear too) shaft that is/was case hardened, outer ring is a dead give away. The little "hook" you kinda see is probably where the failure started.

The innards look different because it is more ductile (softer) than the outer ring. The outer ring snapped quickly compared to the innards which took a teeny bit longer to fully fail.

It also failed right where the shaft necks down where the greatest amount of stress will always occur.

I'd say this was over stressed at some point in its life and whatever you were doing at that moment, was the "last straw". It could have been 60 hours ago where you bounced really hard or caught something that stopped you abruptly that started that small fracture. Not saying you beat your equipment by any means but it's a tractor, it will break, you will fix it and move on.

Me personally, I'd be glad it was the axle that broke and not your actual rear end casting.

Sent from my SM-G920V using Tapatalk
 

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Machining/ Tool & die background here...

It doesn't look like a casting to me. Doubt they use a casting for shaft material, bar stock is cheaper and easier to work with for shafts and heat treats better. Also more "standardized" with grades than castings.

That metal resembles a torsionally stressed (maybe a little bit of shear too) shaft that is/was case hardened, outer ring is a dead give away. The little "hook" you kinda see is probably where the failure started.

The innards look different because it is more ductile (softer) than the outer ring. The outer ring snapped quickly compared to the innards which took a teeny bit longer to fully fail.

It also failed right where the shaft necks down where the greatest amount of stress will always occur.

I'd say this was over stressed at some point in its life and whatever you were doing at that moment, was the "last straw". It could have been 60 hours ago where you bounced really hard or caught something that stopped you abruptly that started that small fracture. Not saying you beat your equipment by any means but it's a tractor, it will break, you will fix it and move on.

Me personally, I'd be glad it was the axle that broke and not your actual rear end casting.

Sent from my SM-G920V using Tapatalk


^^^^What he said^^^^
 

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The depth of the hardened OD could likely only be achieved by using Induction Heat Treating.
The minimum carbon content required for that would likely be a 1045 type steel or possibly at a little more cost 4140.
Can't tell from the picture with the paint on it but these materials could be cast or possibly made from bar stock.
When the greatest strength is required I used to make class 8 truck kingpins by the tens of thousands for Rockwell and Eaton and these pins were made from 4140 and through hardened to 30 Rc then induction hardened with at least .080 case depth of 60 Rc.
The quenching process introduces great stress as you take the more than red hot steel and rapidly cool it to transform the structure and make it hard.
When furnace hardening to get the through hardness the parts are quenched in hot oil. After this they go into a tempering furnace where the temperature of this process will govern the target hardness.
This first furnace operation was normally the one to reveal any "bad" steel that contained inclusions and cracked in the quench process.
When we induction hardened the part was rotated through the inductor where it immediately became "red" hot to our target depth and just a second later passed through a ring that sprayed a water and polymer mixture on the part to quench it, followed by yet another furnace stress relieve soaking then air cool.

It is also possible that induction hardening alone is used to produce this axle.
I would speculate the failure would be caused by several possibilities listed in order of my opinion of likelihood. ( while I did this for years, this does not make me expert in any manner)

1, contaminated raw material
2, fault occurred in the quench sequence
3, stress relieve process was inadvertently skipped on this part
4, shock loading above the design parameters during use, which I really doubt
 

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The depth of the hardened OD could likely only be achieved by using Induction Heat Treating.
The minimum carbon content required for that would likely be a 1045 type steel or possibly at a little more cost 4140.
Can't tell from the picture with the paint on it but these materials could be cast or possibly made from bar stock.
When the greatest strength is required I used to make class 8 truck kingpins by the tens of thousands for Rockwell and Eaton and these pins were made from 4140 and through hardened to 30 Rc then induction hardened with at least .080 case depth of 60 Rc.
The quenching process introduces great stress as you take the more than red hot steel and rapidly cool it to transform the structure and make it hard.
When furnace hardening to get the through hardness the parts are quenched in hot oil. After this they go into a tempering furnace where the temperature of this process will govern the target hardness.
This first furnace operation was normally the one to reveal any "bad" steel that contained inclusions and cracked in the quench process.
When we induction hardened the part was rotated through the inductor where it immediately became "red" hot to our target depth and just a second later passed through a ring that sprayed a water and polymer mixture on the part to quench it, followed by yet another furnace stress relieve soaking then air cool.

It is also possible that induction hardening alone is used to produce this axle.
I would speculate the failure would be caused by several possibilities listed in order of my opinion of likelihood. ( while I did this for years, this does not make me expert in any manner)

1, contaminated raw material
2, fault occurred in the quench sequence
3, stress relieve process was inadvertently skipped on this part
4, shock loading above the design parameters during use, which I really doubt
This was an informative post for me from a heat treatment point of view. Thank you.

Sent from my SM-G920V using Tapatalk
 

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Dang.
Like the others, don't recall an axle snap on this forum before. Unfortunately you are the first.

But i have seen it on a full size backhoe. Watched a guy on a 2wd Case trying to load out of a hard face with front bucket. He would have the back tires jumping back and forth doing burn outs. It was his own backhoe so we would just shake our heads at the abuse he was doing to it. Finally an axle snapped. He looked at us standing there like "what happened?"
Just broke an axle you dope. :laugh:
 
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