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HOUSING 0878495 - Caterpillar

0878495 HOUSING Caterpillar parts HOUSING
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Caterpillar 0878495 HOUSING

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Illustration 3 g03717345
Propel Hydraulic System Reverse Travel (1) Forward solenoid (2) Reverse solenoid (3) Metering spool (4) Forward multifunction valve (5) Pressure limiter (6) Main relief valve (7) Makeup valve (8) From auxiliary hydraulic system (9) Parking brake cylinder (10) Final drive (11) From auxiliary hydraulic system (12) Shift cylinder (13) Servo piston (14) Left propel pump (15) To cooler bypass manifold port "A" (16) From hydraulic tank suction return filter (17) Charge pump (18) Charge relief valve (19) Reverse multifunction valve (20) Left propel motor (21) Flushing relief valve (22) Flushing spool (23) To port "E" of cooler bypass manifold (24) Motor output shaft (25) To left front-wheel assist motor port "F" (26) To right propel pump port "M1" (27) To right propel pump port "M2"When the machine is traveling in reverse, the reverse solenoid (2) is energized. The condition of the reverse solenoid is determined by the signal that is sent from the transmission ECM. The transmission ECM analyzes the input signals to determine the magnitude of the output signal which is then sent to the reverse solenoid.Charge pressure flows across reverse solenoid (2) 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 (13). The charge oil causes the servo piston to shift. This shift changes the angle of the swashplate in left propel pump (14), and the pump generates flow in the reverse circuit. While the machine is traveling in reverse, the following occurs:
Reverse multifunction valve (19) limits system pressure.
Oil from the forward circuit flows through flushing spool (22) .
Makeup valve (7), in forward multifunction valve (4), allows charge oil to flow into the forward circuit.When the propel system is in the travel mode and the parking brake is off, the transmission ECM energizes the shift solenoid. The transmission ECM also energizes the brake solenoid. Oil from auxiliary system (8) and (11) is directed into parking brake cylinder (9), and into shift cylinder (12), respectively. The pressure in these cylinders overcomes the spring forces. These conditions cause the parking brakes to release and the final drive to shift. Under these conditions, the machine operates in the travel-speed range.
Illustration 4 g03717355
Front-wheel Assist System Freewheel (28) Freewheel check valve (29) Freewheel control spool (30) Front-wheel assist manifold (31) Flow divider (32) Flow divider (33) Minimum pressure valve (34) Front-wheel assist solenoid (35) To return manifold port "E" (36) Left rear motor (37) Right rear motor (38) Left front motor (39) Right front motor (40) From right propel charge pump (41) To return manifold port "B" (42) From left propel charge pump (43) To case manifold port "D" (44) Actuator piston (45) From hydraulic tank port "3" (46) Bias spring (47) Front-wheel assist pump (48) Flow compensator spool (49) Pressure compensator spoolWhen the engine is operating, the propel charge pumps and front-wheel assist pump (47) generate flow. Flow from charge pumps (40) and (42) is directed into the case drain of front-wheel assist

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