mechanist
Guest
Had one go on my older 1480- the high pressure relief valve (pilot actuated) threw a circlip that retains the piston operating the relief valve. Valve is located on the hydro motor, where the lines connect. I think there are a variety of reasons that they could go... pretty precision device with no filters except on the charge side. One chunk comes off something, it can bomb the whole chicken coop in hardly any time. The oil is really moving in the circuit. I would get a pressure gauge in the circuit and check the relief pressure first. Does the surging change in relation to the speed if you go slow in different gears, or does it stay the same relative to your ground speed in all gears. Surging same in all gears relative to speed equals problem after the hyd motor. If surging changes, then it would be in the hyd circuit, but the motor should be turning too fast for surging to be evident. I would suspect the relief or something else.