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 94 of 481
TM 9-2320-272-10
1-77
1-21. CONTROL SYSTEM OPERATION (Contd)
TRANSMISSION POWER TAKEOFF (PTO) CONTROL
- A manually
operated control lever located inside the vehicle cab that permits engagement
or disengagement of the transmission Power Takeoff (PTO).
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 driving
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 it to the
control valve.
HYDRAULIC OIL RESERVOIR
- Storage tank for hydraulic oil.
DUMP BODY SAFETY LATCH
- Hydraulically-operated in conjunction
with the dump body control lever, the safety latch locks the dump body in the
lowered position and releases it when the control lever is pulled back to the
raised position.
DUMP BODY CYLINDER ASSEMBLY
- Consists of two piston-type
hydraulic cylinder hoists. Assembly raises and lowers dump body with
hydraulic oil, forcing the cylinder upward or downward.
OIL FILTER
- Filters used or bypassed oil from the control valve before it
returns to the hydraulic oil reservoir.
CONTROL VALVE
- Four-port valve accepts pressurized oil from the
hydraulic pump and directs oil pressure flow from control valve to the
hydraulic cylinders. It also directs oil returning from the hydraulic cylinders
back to the hydraulic oil reservoir.
DUMP BODY CONTROL LEVER
- An operator control that determines
the hydraulic oil pressure flow from control valve to the hydraulic cylinders.
The route this oil takes will determine whether the dump will raise or lower.
CONTROL LINKAGE
- Connects dump body control lever inside cab to the
control valve.
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