SEAT GP-SUSPENSION 1111902 - Caterpillar

Reverse Drive Position
Speed shift switch (25) is in the center position and no current flows to speed shift valve (29). The speed shift spools in the rear motors are connected to the hydraulic tank and the motors are in the low speed position. Parking brake switch (7) is released (pulled up) and current flows to parking brake valve (30). The valve spool moves up and allows charge oil to release the parking brakes and to go to directional control solenoid (32).When the propulsion control lever is moved toward the rear, direction control potentiometer (5) is rotated and allows current to flow to the solenoid on the right end of the directional control solenoid. The directional control valve spool moves to the left. The oil goes to the left end of pump control (14) and moves the pump swashplate which causes high pressure oil to flow from port B to line (22). Pressure oil in loop line (22) flows to flow divider valve (24). Oil flows through the flow divider valve to rear drive motors (10) and (17). Oil flow to the two motors is in parallel. Oil leaves the drive motors and returns to pump (15) through loop line (13).The check valve section of relief valve (21) will close when oil is pumped along loop line (22). The check valve section of relief valve (12) will open to allow oil from the charge pump circuit to enter the loop line. This will compensate for internal leakage within the different circuit components. Oil from the case of motors (10) and (17), and pump (15) is sent back to the tank through return lines.Main loop line relief valve (21) remains closed. If the pressure of the oil in the feed line reaches the same value as the setting of the valve, the valve will open and allow oil to flow through the check valve of relief valve (12) and into return line (13) of the closed circuit.When the propulsion control lever is moved farther toward the rear, there is an increase in current flow to the directional control solenoid. This causes the valve spool to move farther to the left. The oil pressure to the pump control increases. This causes the swashplate angle to increase and there is an increase in pump flow to the drive motors.Speed limiter potentiometer (1) can be set to limit the maximum current flow to the direction control solenoid. This limits the maximum speed in forward or reverse direction.High Speed
Speed shift swith (25) is in the right hand position and current flows to speed shift valve (29). The speed shift valve spool moves down and connects the speed shift spools in the rear motors to charge oil in line (33). The rear motors are in small displacement, high speed position. Parking brake switch (7) is released (pulled up) and current flows to parking brake valve (30). The valve spool moves up and allows charge oil to release the parking brakes and to go to directional