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 90 of 481
TM 9-2320-272-10
1-73
1-21. CONTROL SYSTEM OPERATION
Oil pressure (hydraulics) is used to provide operating power for the auxiliary
equipment on the vehicles covered in this manual. The components that provide
hydraulic power are discussed in the following order:
a.
Front Winch Hydraulic System Operation (page 1-73).
b.
Rear Winch Hydraulic System Operation (page 1-74).
c.
Body Hydraulic System Operation (page 1-76).
d.
Medium Wrecker Crane Hydraulic System Operation (page 1-78).
a.
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:
TRANSMISSION POWER TAKEOFF (PTO) CONTROL
- A manually
operated control lever located inside the cab that permits engagement or
disengagement of the transmission Power Takeoff (PTO).
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.
TRANSMISSION POWER TAKEOFF (PTO)
- Uses driving power of the
transmission to provide mechanical driving power for the hydraulic pump.
POWER TAKEOFF (PTO) DRIVE SHAFT
- Transmits mechanical power
from the PTO to the hydraulic pump.
HYDRAULIC PUMP
- Driven by the PTO drive shaft, it draws oil from the
oil reservoir through hydraulic hoses, then pressurizes and directs this oil to
the control valve.
E
D
C
B
A
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