TM 9-2320-272-24-1
1-24. HYDRAULIC SYSTEM OPERATION (Contd)
b. Rear Winch Hydraulic System Operation.
A rear winch is installed only on the M936/A1/A2 medium wrecker. It is used primarily to rescue vehicles
that have become deeply mired. The rear winch hydraulic system converts mechanical power of the engine
into fluid power through use of the hydraulic pump and back into mechanical power at the winch drive
motor. The major components of the rear winch hydraulic system are:
Key Item and Function
1 TRANSFER CASE PTO CONTROL - A manually-operated control lever located inside the cab that
permits engagement or disengagement of the PTO.
2 TRANSFER CASE PTO - Uses driving power of the transfer case to provide mechanical driving
power for the hydraulic pump.
3 PTO DRIVESHAFT - Transmits mechanical driving power from PTO to the hydraulic pump.
4 HYDRAULIC PUMP - Draws oil from hydraulic oil reservoir and directs it to the rear winch
control valve and winch drive motor.
5 OIL FILTER - Filters used or bypassed oil from the control valve before it returns to the hydraulic
oil reservoir.
6 HYDRAULIC OIL RESERVOIR - Storage tank for hydraulic oil.
pulled outward to HIGH for heavy loads or pushed inward to LOW for light loads.
8 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.
9 DIRECTIONAL CONTROL VALVE - Receives pressurized hydraulic oil from the hydraulic pump
and directs it to the winch motor. The flow of 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.
winch drum clutch in high or low gear range.
11 WINCH MOTOR - Converts hydraulic power back into mechanical power needed to turn the rear
winch drum.
12 CONTROL LINKAGE - Connects transfer case PTO control to transfer case PTO.
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