oldnslo
Super Member
Modrob
Closed loop hydrostatic drives require a separate charge pump to maintain a minimum “charge” pressure in the “closed loop” circuit.
Closed loop is where oil exits the pump and connects directly to a motor or motors. The outlet of the motor(s) connects back to the other work port on the pump. Since this circuit does NOT connect to the reservoir it requires make up oil to replace leakage losses or the charge circuit.
Some styles of motors used in closed loop applications have an external case drain which allows oil that leaks to drain to tank at low pressure so a high pressure shaft seal is not required. Per Moss Road your machine did not have that feature.
The hydrostatic pump does have a case drain to allow leakage past slippers, pistons, etc. to drain directly to tank. Typically case pressure should be less than 30 PSI to protect the shaft seal.
Typical cause of the slippers being pulled off the pistons is loss of charge pressure causing the slippers to lift off the swash plate.
High case pressures can also cause slipper lift off but that is more common on open loop applications.
Either way I agree most likely not cost effective to rebuild that old of a machine since I would be very surprised if the wheel motors are not damaged.
Closed loop hydrostatic drives require a separate charge pump to maintain a minimum “charge” pressure in the “closed loop” circuit.
Closed loop is where oil exits the pump and connects directly to a motor or motors. The outlet of the motor(s) connects back to the other work port on the pump. Since this circuit does NOT connect to the reservoir it requires make up oil to replace leakage losses or the charge circuit.
Some styles of motors used in closed loop applications have an external case drain which allows oil that leaks to drain to tank at low pressure so a high pressure shaft seal is not required. Per Moss Road your machine did not have that feature.
The hydrostatic pump does have a case drain to allow leakage past slippers, pistons, etc. to drain directly to tank. Typically case pressure should be less than 30 PSI to protect the shaft seal.
Typical cause of the slippers being pulled off the pistons is loss of charge pressure causing the slippers to lift off the swash plate.
High case pressures can also cause slipper lift off but that is more common on open loop applications.
Either way I agree most likely not cost effective to rebuild that old of a machine since I would be very surprised if the wheel motors are not damaged.