TM-9-2320-272-23-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5
SEPTEMBER 2012
TM-9-2320-272-23-1 - Page 257 of 1313
FRONT WINCH HYDRAULIC SYSTEM OPERATION
A front winch is installed on M925/A1/A2, M928/A1/A2, M930/A1/A2, M932/A1/A2, and M936/A1/A2 series vehicles.
The front winch hydraulic system converts mechanical power at the winch drive motor. The basic operating principles
are the same for each model. Major components of this system are:
A. WINCH CONTROL LEVER
- An operator control that determines the hydraulic oil pressure flow from the
control valve to the winch motor. The flow of this oil determines the direction the winch drum will turn.
B. TRANSMISSION PTO
- Uses transmission driving power to provide mechanical driving power for the
hydraulic pump.
C. PTO DRIVESHAFT
- Transmits mechanical power from PTO to the hydraulic pump.
D. HYDRAULIC PUMP
- Driven by PTO driveshaft, it draws oil from the oil reservoir through hydraulic hoses,
then pressurizes and directs this oil to the control valve.
E. OIL FILTER
- Filters used or bypassed oil from the control valve before it returns to the hydraulic
oil
reservoir.
F. HYDRAULIC OIL RESERVOIR
- Storage tank for hydraulic oil.
G. CONTROL VALVE
- Four-port valve accepts pressurized oil from the hydraulic pump and directs this oil
to the winch motor. It also directs oil returning from the winch back to the oil reservoir. The flow of this oil
from the valve determines the directional drive of the winch motor.
H. WINCH MOTOR
- Converts hydraulic power into mechanical power as hydraulic oil is forced through the
winch motor.
I. CLUTCH LEVER
- Manual control that engages winch drum gear to drive gear of winch motor.
J. TRANSMISSION PTO CONTROL
- A manually-operated control lever located inside the cab that permits
engagement or disengagement of the transmission PTO.
I
H
G
J
A
B
C
D
E
F
G0046DAA
Figure 34.
Front Winch Hydraulic System Components.
TM 9-2320-272-23-1
0003
0003-52
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