BRACKET AS 3438677 - Caterpillar

Components
A. Propel PumpThe propel pump is a variable-displacement piston-type pump which provides hydraulic oil to the propel system. The pump is mounted to a double-pump drive, and is driven by the machine engine. The propel pump contains a charge pump, which supplies charge oil to the system.B. Charge FilterCharge oil for the propel system leaves the charge pump and passes through this filter before entering the propel pump. The charge filter has a 6 micron replaceable element, and is equipped with a bypass valve. A pop-up indicator on top of the filter can be used to monitor filter condition. C. Rear Propel MotorThe rear propel motor is a variable-displacement piston-type motor. High-pressure oil from the propel pump is routed to the rear propel motor. The motor provides propulsion through rear axle (E) to the rear wheels of the machine.The displacement of the motor can be set in either HIGH or LOW, using the speed range shift switch.D. Relief Valve BlockHigh-pressure oil to the propel motor, and low-pressure return oil from the propel motor are both routed to the relief valve block. This block contains two high-pressure relief valves, a shuttle valve, and a low-pressure relief valve. These parts are installed in an aluminum manifold.The relief valve block has two purposes. It monitors the pressure in the system, protecting components from excessive pressure. It also allows some low-pressure return oil to flow back to the hydraulic oil tank. This allows fresh charge oil to continually enter the closed-loop system.E. Rear AxleThe rear propel motor delivers power to the axle through a gear reducer. The axle contains a no-spin differential and planetary wheel ends. This drives the rear wheels and propels the machine. The axle used depends on the serial number of the machine (see Parts Book). The gear reducer may be part of the axle or a separate component, depending on the serial number of the machine.F. Solenoid ValveThe solenoid valve is located behind the hydraulic oil tank in the engine compartment, and is wired to the speed range shift switch. The solenoid valve routes charge oil to the servo-pistons on the propel motor. This sets the speed range of the machine in HIGH or LOW.G. Propel LeverThe propel lever is located to the right of the operator's seat, and is mechanically connected to the propel pump. By moving the propel lever forward or backward, the operator sets the displacement of the propel pump. This determines the direction and speed of the machine.H. Speed Range Shift SwitchOn machines with serial number 6ZD1-185, the speed range shift switch is located on the instrument panel to the left of the operator's seat. On machines with serial number 6ZD186-up, the speed range shift switch is located on the propel lever. The operator uses this switch to set the speed range of the machine, in LOW or HIGH.Operation
Center/Stop
1. Hydraulic oil is drawn into the charge pump from the hydraulic oil tank.2. The charge pump puts this oil under pressure. Charge oil exits the