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| Illustration 1 | g01514981 |
(1) 283-7728 Piston Pump Gp (ALL WHEEL DRIVE) (2) Solenoids (3) Input shaft (4) 273-5454 Piston Pump Gp (ALL WHEEL DRIVE) (5) Ports for oil flow (6) Solenoids (7) Ports for oil flow | |
The All Wheel Drive piston pumps (AWD pumps) (1) and (4) are variable displacement axial piston pumps. Piston pumps (1) and (4) are fastened to the engine. The flywheel in the engine drives the input shafts for the piston pumps. Input shaft (3) turns the barrel assembly and the nine pistons. Piston pumps (1) and (4) are assembled as a tandem unit.
AWD piston pumps (1) and (4) are controlled by the All Wheel Drive Electronic Control Module (AWD ECM). The AWD ECM receives inputs from the following:
- The transmission speed sensor
- The speed sensors for the AWD motors
- The AWD control switch
- The AWD aggressiveness control dial
The AWD ECM will interpret the inputs. The AWD ECM will send a signal to solenoid valves (2) and (6). If the AWD ECM determines that more speed is required of the front wheels, the solenoid valves will upstroke the pumps. If the AWD ECM determines that less speed is required of the front wheels, the solenoids will destroke the pumps.
The AWD ECM will control the amount of oil flow and the direction of oil flow from the piston pumps. The pump control valve will control the direction of the swashplate and the angle of the swashplate. When charge oil is sent to two of four actuator pistons, the swashplate will change angles. The tilted swashplate causes the pistons to move in and out of the barrel assembly. As the barrel assembly turns, the movement of the pistons causes oil flow from either port (5) or port (7). The pressure override circuit (POR) and the two main relief valves limit the output pressure of the pumps.