# Hydraulic pump drive shaft



## pigslaer (May 29, 2016)

1995 555D ford New Holland back hoe hydraulic pump drive shaft - Broke the hub that connects to engine crank shaft. the universal joints also broke and looked as if they had never been greases. they got blamed for the failure of the hub.
installed all new parts and it broke again in the same manner. Inspected pump and found no reason for the failure. any suggestions will be very welcome.


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## sixbales (May 18, 2011)

Howdy piglaer, welcome to the Ford tractor forum

Have you checked the shaft for misalignment between crankshaft pulley and pump? Possibly harmonic failure?? 

You inspected the pump and found no reason for a failure. You might consider having a hydraulic shop inspect it as a double check. 

I would put a 5000 psi pressure gauge on the pump output. If it exceeds 2500 psi, you have a blockage somewhere. You might consider installing a pressure relief valve on the system first, so you don't break things up again, while trying to isolate the problem. There should be a safety valve already in the system. Obviously not working, or the blockage is before it.

Does the pump itself have a safety bypass valve? Do you hear fluid squeal at any time?


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## sixbales (May 18, 2011)

I read on the internet that each section of a Ford backhoe valve has its own relief and then there is a main relief for the whole valve. Don't know if this is true and correct, but if so, a blockage (essentially deadheading the pump) has to occur before fluid gets to the backhoe valves. I guess I would check the loader valve for a blockage...


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## sixbales (May 18, 2011)

Sometimes old hydraulic hoses disintegrate internally and cause a blockage.


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## TraderMark (Nov 15, 2011)

Did you make sure the two halves of the driveshaft were in phase when you installed the new u-joints? Out of phase shafts are the most common cause of premature u-joint failure.


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