I've seen the key shear off between the pump gear and shaft on high-hour 9600's (similar pump) but never seen a shaft fail. Either the shaft was faulty (improper hardening at the factory, etc) or there was a pressure spike on the system. Make sure you check system pressures after installing the new pump.
Pump failures are very typical on all 9000 seres walker and STS-except latest combines have been updated which is what you will get from parts providing they do no sell old stock-----updated pump is a now two pumps and housing and different hardware---------We probly have 5 pumps in stock
Had an 07 9660 fail the shaft last fall, it had around 800 sep. Put another 100 on without anymore issues. Also on an other machine blew the seal between the pumps causing the oil to overflow the reservoir. That happened the last day of harvest. We stock the hydraulic pump because they just seem to go at any time, no rhyme or reason. It had been two seasons since we had one go out and it will probably be two more before it happens again. At least you can change one very timely.
JUst thought I had a lemon coz I have had two pump failures in two seasons on top of the fires. It happens as you turn and hit full lock. The last pump is the steering pump . So I guess the pressure release valve is the problem and is not releasing at correct pressure hence overloading the pump . Next question is where do I find the valve on 9660sts?