HOSE AS 8W5159 - Caterpillar

Illustration 2 g06023026
Hydraulic Schematic FORWARD
(1) Right propel motor
(2) Park brake
(3) Motor solenoid
(4) Park brake
(5) Motor solenoid
(6) Left propel motor
(7) Final drive
(8) Brake dump valve
(9) Return manifold
(10) Oil cooler
(11) Flushing relief valve
(12) Flushing spool
(13) Propel pump
(14) Combination valve
(15) Combination valve
(16) Case relief valve
(17) Line from charge relief
(18) Motor servo piston
(19) Final drive
(20) Flushing relief valve
(21) Flushing spool
(22) Motor servo piston
(23) Line from charge filter
(24) Needle valve
(25) Right reverse solenoid
(26) Right forward solenoid
(27) Pump servo piston
(28) Combination valve
(29) Combination valve
(30) Manual brake release
(31) Needle valve
(32) Left reverse solenoid
(33) Left forward solenoid
(34) Pump servo piston
(35) Interlock solenoidThe above illustration shows the propulsion hydraulic system under the following conditions:
The parking brake switch in the OFF position
The propel gear setting is set to first gear
The machine traveling forwardCharge oil is directed to charge relief valve (17), to combination valves (14), (15), (28) and (29), and to interlock solenoid (35). With the parking brake switch in the OFF position, the interlock solenoid directs charge oil to propel pump (13) directional solenoids (25), (26), (32) and (33). Oil is also directed into the piston cavities of parking brakes (2) and (4). The charge pressure in the parking brake piston cavities overcomes the spring force, and the parking brakes release.When the propel gear setting is set to first gear, motor solenoids (3) and (5) are not energized. In this case, propel motors (1) and (6) remain at the maximum displacement angle.When the machine ECM determines that the machine should be moving forward, the ECM energizes left forward solenoid "C2" (33) and right forward solenoid "C2" (26). In this case, the solenoids direct charge oil into the forward side of pump servo pistons (27) and (34). The pressure in the forward side of the servo pistons causes the pump servos to move. This movement changes the angle of the swashplate in each rotating group of the pump. The stronger the signal to the solenoids, the greater the swashplate angle, and therefore, the greater the oil flow from the propel pump.As the swashplates move, the feedback linkages tend to move the pump solenoid spools back to neutral through internal feedback springs. This action prevents the servo pistons from tilting the swashplates too far.Supply oil from the left section of propel pump (13) flows to the following locations:
Forward combination valve (15)
Port "B" of left propel motor (6)The pressure differential between the forward and reverse sides of left propel motor (6) causes the motor to turn. After turning the motor, oil at a reduced pressure flows to the following locations:
The reverse side of the motor
Flushing spool (12) in the left propel motor
The left motor flushing relief valve (11)
Port "A" of propel pump (13)Supply oil from right section of propel pump (13) flows to the following locations:
Forward combination valve (29)
Port "B" of right propel motor (1)Right propel motor (1) turns. Reduced pressure oil flows to the reverse side of the motor, to right motor flushing spool (21) and flushing relief valve (20), and to port "C" of propel pump (13).The balance line