HYDRAULIC 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. Dump Body Hydraulic System Operation (page 1-76).
d. Medium Wrecker Crane Hydraulic System Operation (page 1-78).
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.