As soon as the swashplates are tilted, the rotating groups
receive the charge oil. The high pressure oil in closed circuit
loop lines goes to each propel motor. The low pressure oil in
closed circuit loop lines leaves each motor and returns to the
pumps, or goes to tank through shuffle valves.
The high pressure oil closes the check valve on the high
pressure side of the closed circuit loop. The low pressure
check valve opens to allow oil from charge circuit oil to enter
low pressure closed circuit loop. This compensates for internal
leakage within the different circuit components.
The high pressure oil in the closed circuit loop moves the
shuttle valve spool inside motor flushing valves (15) and (16).
Hot low pressure oil flows from the flushing valves to the relief
motor shuttle valves. This allows fresh charge oil to enter the
low pressure side of the loop through the pump checks.
The high pressure relief valves protect the system from sudden
high pressure spikes. When the differential pressure is above
the high pressure relief valves setting, the valves route the oil
to the low pressure loop.
Oil from the case of the axle pump goes to the case of the
drum pump, and to hydraulic oil tank (12). Oil from the case of
drum drive motor and axle motor goes to thermal bypass valve
When the speed selector switch on the operator console is in
the HIGH speed position, the speed shift control valve is
energized. The valve spool moves to the right. In this position
the speed shift spool in each propel motor is supplied with
charge oil. Each motor is in minimum (small) displacement