JD 4720 Hydraulic Failure

[arlen4720]

I am not seeing how one pump caused total hyd failure.

A dead implement pump would not affect the transmission.

If it has a steering pump, it should still work.

The steering pump and implement pump are a stacked unit driven from a common shaft. The steering pump supplies charge flow to the hydrostat pump, so shear the coupling, and no implement, no steering, no charge flow, no hydrostat.

 

[J_J]

Thanks, I learned some things today.

 

[blackfalcon]

I asked the same question. The guys at the dealership said they had never seen that happen before and assumed it was a defect.

 

[J_J]

You might think back about what might have caused the shaft to strip.

You might consider that maybe a QD became disconnected and deadheaded the pump, and the shaft was the weakest point.

Maybe the pump mounting bolts were loose.

Are you saying that the guys at the tractor place have never seen a stripped pump shaft?

It is a defect alright, but something caused it.

You might ask to look at all the service bulletins.