SEAL-DUST 1404016 - Caterpillar

Illustration 4 g06058977
Propulsion Hydraulic System Reverse Travel
(1) Reverse solenoid
(2) Forward solenoid
(3) Metering spool
(4) To right front-wheel assist motor port"F"
(5) Reverse multifunction valve
(6) Pressure limiter
(7) Main relief valve
(8) Makeup valve
(9) Final drive
(10) From auxiliary hydraulic system
(11) Parking brake cylinder
(12) Servo piston
(13) Right propulsion pump
(14) To cooler bypass manifold port"B"
(15) From hydraulic tank suction return filter
(16) Charge pump
(17) Charge relief valve
(18) Forward multifunction valve
(19) To left propulsion pump port"M2"
(20) To right propulsion pump port"M1"
(21) Right propulsion motor
(22) Flushing relief valve
(23) Flushing spool
(24) Shuttle valve
(25) Speed valve
(26) From auxiliary manifold port"FDS"
(27) Servo piston
(28) To cooler bypass manifold port"J"
(29) Motor output shaftWhen the machine is traveling in reverse, reverse solenoid (1) is energized. The transmission ECM analyzes the input signals to determine the magnitude of the output signal that is sent to the reverse solenoid.Charge pressure flows across reverse solenoid (1) and acts against metering spool (3). The metering spool moves, and charge oil is metered across the spool to the reverse chamber of servo piston (12). The charge oil causes the servo piston to shift. This shift changes the angle of the swashplate in propulsion pump (13), and the pump generates flow in the reverse circuit.While the machine is traveling in reverse, the following occurs:
Reverse multifunction valve (5) limits system pressure.
Oil from the forward circuit flows through flushing spool (23).
The makeup valve, in forward multifunction valve (18), allows charge oil to flow into the forward circuit.When the propulsion system is in the travel mode and the parking brake is off, the transmission ECM energizes the shift and brake solenoids. Oil from auxiliary system (10) and (26) is directed into parking brake cylinder (11) and to speed valve (25), respectively. The pressure in parking brake cylinder overcomes the spring force. These conditions cause the parking brakes to release. The pressure acting against the speed valve causes the valve to shift. This shift opens a passage for reverse circuit oil to flow into the head end of servo piston (27). Since the effective area of the head end of the servo piston is greater than the effective area of the rod end, the piston extends. Under these conditions, the propulsion motor operates at minimum displacement, and the machine operates in the travel-speed range.Front-Wheel Assist
Illustration 5 g06058822
Front-wheel Assist System Freewheel
(1) Front-wheel assist manifold
(2) Freewheel check valve
(3) Freewheel control spool
(4) Flow divider
(5) Minimum pressure valve
(6) Front-wheel assist solenoid
(7) To return manifold port"E"
(8) Left rear motor
(9) Right rear motor
(10) Left front motor
(11) Right front motor
(12) From right propulsion charge pump
(13) To return manifold port"B"
(14) From left propulsion charge pump
(15) To hydraulic tank port"6"
(16) Actuator piston
(17) From hydraulic tank port"3"
(18) Bias spring
(19) Front-wheel assist pump
(20) Pressure compensator
(21) Flow compensatorWhen the engine is operating, the propulsion charge pumps and front-wheel assist pump (19) generate flow. Flow from charge pumps (12) and (14) is directed into the case drain of front-wheel assist motors (8), (9), (10), and (11).Downstream from front-wheel assist motors (8), (9), (10), and (11), case drain oil is combined. The combined oil is directed into port"CD2" of the