TM-9-2320-272-10
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; OPERATOR'S MANUAL
SEPTEMBER 2004
CHANGE 2
TM-9-2320-272-10 - Page 92 of 481
TM 9-2320-272-10
1-75
1-21. CONTROL SYSTEM OPERATION (Contd)
TRANSFER CASE POWER TAKEOFF (PTO) CONTROL
- A manually
operated control lever located inside the cab that permits engagement or
disengagement of the Power Takeoff (PTO).
TRANSFER CASE POWER TAKEOFF (PTO)
- Uses driving power of the
transfer case to provide mechanical driving power for the hydraulic pump.
POWER TAKEOFF (PTO) DRIVE SHAFT
- Transmits mechanical driving
power from PTO to the hydraulic pump.
HYDRAULIC PUMP
- Draws oil from hydraulic oil reservoir and directs it
to the rear winch control valve and winch drive motor.
OIL FILTER
- Filters used or bypassed oil from the control valve before it
returns to the hydraulic oil reservoir.
HYDRAULIC OIL RESERVOIR
- Storage tank for hydraulic oil.
TORQUE CONTROL LEVER
- Controls the operating gear ratio of the
winch drive motor. Lever is pulled outward to HIGH for heavy loads or
pushed inward to LOW for light loads.
WINCH DIRECTIONAL CONTROL LEVER
- Manually-operated lever
that controls the WIND and UNWIND direction of the rear winch drum.
Lever does this by opening and closing the directional control valve to the
winch motor, and reversing the direction of pressurized hydraulic fluid. Lever
is pushed inward to wind and pulled outward to unwind winch cable.
DIRECTIONAL CONTROL VALVE
- Receives pressurized hydraulic oil
from the hydraulic pump and directs it to the winch motor. The flow of the
hydraulic oil to and from this control valve provides forward or reverse
driving power to the winch motor. Valve also returns used oil back to the
hydraulic oil reservoir from the winch.
TORQUE CONTROL VALVE
- Hydraulically controls the hydraulic oil
pressure to engage rear winch drum clutch in HIGH or LOW gear range.
WINCH MOTOR
- Converts hydraulic power back into mechanical power
needed to turn the rear winch drum.
CONTROL LINKAGE
- Connects transfer case power takeoff control to
transfer case power takeoff.
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