What could have caused this Hydraulic Pump shaft to shear off like this???

I found out why my TB135 hydraulics ceased to function all at once. The hydraulic pump shaft sheared off and I'm puzzled as to what could have caused it. The bolt were tight joining it to the engine. Anybody had that to occur before? This is gonna be super expensive to repair.....gonna call dealer tomorrow and price a new pump...this is not gonna be pretty i'm sure. From the looks of it, it appears to have been holding by a narrow thread.....what kind of trauma could have caused this vice the coupler failing first?

Does pump turn? Was pump mounted correctly,tight. Any play where shaft mounts to engine?

How about a close up of both broken ends? from this distance it looks like a sudden shock overload, but I'm not an expert and that's not a good enough picture. Easy enough to find metal failure mode pictures, that show what different breaks look like.

You might find the pump is rebuildable, or it might have grenaded inside and the whole machine is contaminated with grenaded pump parts, and you're better off selling it for rebuildable parts.

Delmer said:

How about a close up of both broken ends? from this distance it looks like a sudden shock overload, but I'm not an expert and that's not a good enough picture. Easy enough to find metal failure mode pictures, that show what different breaks look like.

You might find the pump is rebuildable, or it might have grenaded inside and the whole machine is contaminated with grenaded pump parts, and you're better off selling it for rebuildable parts.

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The machine was running fine up til break. I just had the pump rebuilt 6 months ago .....actually a seal kit. Contemplating pricing a new shaft...but then I gotta buy another new seal kit plus labor to rebuild......hmmmmn....this pump is 16 years old. Maybe time to invest in a new pump....crying!

Looks

Delmer said:

How about a close up of both broken ends? from this distance it looks like a sudden shock overload, but I'm not an expert and that's not a good enough picture. Easy enough to find metal failure mode pictures, that show what different breaks look like.

You might find the pump is rebuildable, or it might have grenaded inside and the whole machine is contaminated with grenaded pump parts, and you're better off selling it for rebuildable parts.

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Looks like it was only hanging on by a thread anyway.....not sure what trauma in was subject to before I bought it but obviously it didn't all happen yesterday from the looks of this break.

I

Bls repair said:

Does pump turn? Was pump mounted correctly,tight. Any play where shaft mounts to engine?

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Pump was tight, not sure if it still turns now....I suspect it does.

Thats a really lousy picture for failure analysis. The rust shows it had been cracked for some time. From what I see, the failure started in the top corner, can't see enough to give a clue why.

terex herder said:

Thats a really lousy picture for failure analysis. The rust shows it had been cracked for some time. From what I see, the failure started in the top corner, can't see enough to give a clue why.

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Sorry about the picture clarity.....I just happened to have taken that picture when I removed it. I don't have a current clearer pic and not at the shop now where I could take another.

Looks like it started in the far left side, and progressed slowly across. Can even see the rust marks off the top.

Much better outlook for the pump and machine as a whole than my earlier mistaken guess.

I wonder if they even looked at that area when the pump was resealed six months ago?

Agree, the marks looks like that fracture was already there, what was left holding just fractured recently. What caused the original stress crack? Who knows at this point.

Is that a Sundstrand pump? If it's just a shaft failure and the pump is otherwise OK, I've got a feeling that you can just remove the shaft and drop a new one in.

If you can get a shaft do that, you won't need new seals if it only has a few months on it. Whatever you decide, make sure you or a good tech checks and sets the pressures on your machine. Could be just metal fatigue but more likely pressure spikes over a period of time did this in. Any chance you have an auxiliary circuit controlled by a solenoid valve? The Folks at Riverside Hydraulics are aces in my book if you need any help they probably can.

That looks like an old Rexroth pump. I don't recognize that control block on the top of the pump. I usually see pumps like that in closed loop hydraulic systems or used as a charge pump. You will have to split the cases and take a look inside. I recently went through a pump like that in a telehandler and found that the rod from the governor to the swash plate popped out of the socket and stuck in this case leaving the pump only partially on stroke. Below is a photo of the reason it happened. Another case of contaminated oil.

You say the pump was resealed 6 months ago, what was the reason and how many hours has it run since the reseal?

I suspect similar that the pump seized and finished the shaft.

Guessing that's a split flow horsepower limiting variable pump from maybe Nachi or the like.

maybe the shaft was stressed during assembly by uneven tightening of the mount bolts, cocking the assy as it was drawn together. on a heavy pump, it is usually preferable to use guide dowels to seat the pump and then remove the dowels and install the bolts if clearance allows otherwise the weight of the pump assy will be carried on the shaft during assembly

Wonder if the pump could have been accidently dropped or something else happened when it was resealed?

Obviously the pump has to come apart. At that time you will be able to determine if pump internals are to blame. I suspect not. What is probably most likely is install or teardown error in which a large bending force was put on the shaft. Most shafts like this are case hardened to get good surface wear properties while still getting good torsional strength. I refer to this as an "m&m". Hard shell, soft center. The issue with this is the outside is brittle and is possible that the case got a crack, but the shaft would not just break off due to the softer core. But once a crack starts, it will propagate.

I caught a similar issue with the input shaft on a final drive. Typical torsion crack because a track brake was loose and ignored. That crack was so small that I would bet many field mechanics would have missed it. I used some of my manufacturing methods to confirm it was indeed a crack, but machine was still working. It would have failed in short order.

As mentioned, it would be critical to properly support the pump. I find that assembly is easier because the shaft won't even go in but on teardown, it can be hard to gauge the proper lifting force.

Heavy Chevy said:

.hmmmmn....this pump is 16 years old. Maybe time to invest in a new pump....crying!

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It has paid for itself several times over and time to let it die peacefully. At this point it doesn't matter what caused it. Just make sure to check pressures after you put the new one in.