LINES GP-DIFFERENTIAL LOCK 4777881 - Caterpillar

Illustration 3 g02646532
Propel Hydraulic System (REVERSE/BRAKE RELEASED/TRAVEL) (1) Forward EDC (2) Reverse EDC (3) EDC metering spool (4) Forwar 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 "F" (16) From hydraulic tank suction return filter (17) Charge pump (18) Charge relief valve (19) Reverse multifunction valve (20) Flushing relief valve (21) Flushing spool (22) To port "D" of cooler bypass manifold (23) Left propel motor (24) Motor output shaft (25) To left FWA motor case drain circuitNote: The following circuit description can be used to discuss either the right or left propel hydraulic circuit.When the machine is traveling in reverse, reverse EDC (2) is energized. The condition of the reverse EDC is determined by the signal that is sent from the machine ECM. The machine ECM analyzes the input signals to determine the magnitude of the output signal which it then sends to the reverse EDC.Charge pressure flows across reverse EDC (2) and acts against EDC metering spool (3). The EDC 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 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 (21)
Makeup valve (7), in forward multifunction valve (4), allows charge oil to flow into the forward circuit.When the propel mode switch is in the TRAVEL position and the parking brake switch is in the OFF position, the machine ECM energizes the shift solenoid, and the machine ECM also energizes the brake solenoid. Oil from auxiliary system (8) and (11) is directed into shift cylinder (12) and into parking brake cylinder (9) respectively. The pressure in these cylinders overcomes the spring forces; this causes the parking brakes to release and the propel motor to shift. Under these conditions, the machine operates in the travel speed range.
Illustration 4 g02646534
Front wheel Assist System Off (FREEWHEEL) (57) To hydraulic tank (58) Auxiliary pump (59) Displacement piston cavity (60) Hydraulic tank port "2" (61) Bias spring (62) Front wheel assist manifold (63) Pilot opened check valve (64) Front wheel assist control solenoid (65) Front wheel assist logic valve (66) To front return manifold (67) Front wheel assist proportional solenoid (68) Steering priority valve (69) Steering priority valve manifold (70) To auxiliary manifold (71) Pressure compensator spool (72) Right rear motor (73) Right front motor (73) From right propel charge pumps (75) From left propel charge pumps (76) To return manifold port "G" (77) Left front motor (78) Left rear motor (79) Freewheel check valve (80) Flow divider (81) Anti cavitation check valves (82) From