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 97 of 481
TM 9-2320-272-10
1-80
1-21. CONTROL SYSTEM OPERATION (Contd)
(2) The major components for raising and lowering the crane cable and hook for
the HOIST action are:
SHEAVES
- Grooved wheels that guide hoist cable through boom.
HOIST MOTOR ASSEMBLY
- Converts hydraulic power back into
mechanical power needed to turn the hoist drum.
UPPER ROLLER ASSEMBLY
- Prevents cable from contacting inner boom
during winding/unwinding.
CRANE HOIST CABLE DRUM
- Is turned by the worm gear in hoist
motor assembly. Drum unwinds cable when turning toward front of vehicle.
Drum winds cable when turning toward rear of vehicle.
HOIST CONTROL LEVER
- Manual control attached to the control valve
that determines hydraulic oil flow for the raising and lowering action of the
crane hoist cable and hook. Lever is pulled back to raise cable and hook and
pushed forward to lower cable and hook.
HOIST CONTROL VALVE
- Two-way hydraulic valve located under the
hoist control lever directs fluid from the hydraulic pump to the hoist motor
assembly and back through the valve to the hydraulic oil reservoir.
F
E
D
C
B
A
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