UNDERCARRIAGE RT880E SERVICE MANUAL
8-10 Published 11-10-2014, Control # 524-00
Hydraulic Pumps
Description
Front Steer
The hydraulic pump is mounted off of drive pads of the
torque converter and driven by the engine. Pump number 2
provides the hydraulic flow necessary to power the front
steer cylinders and the swing drive system. The pump is a
gear type pump that provides a flow of approximately
38.9 gpm (147 l/min).
Rear Steer
The hydraulic pump is mounted to the torque converter and
is driven by the engine. Pump number 1 provides the
hydraulic flow necessary to power all crane function except
front steer and swing. The pump is a piston type pump that
provides a flow of approximately 98.7 gpm (373 l/min).
Front Steering Control Valve
Description
The steering control valve is located under the dash and is
actuated by a conventional steering wheel and steering
column, providing precise, full hydraulic steering. Precise
steering is accomplished by a metering system within the
valve that is directly connected to the steering column and
wheel.
Maintenance
Removal
1. Thoroughly clean the steering control valve and the sur-
rounding area before removing the hydraulic hoses from
the valve.
2. Tag and disconnect the five hydraulic hoses from the
steering control valve. Cap or plug each hose and the
five ports of the valve.
3. Remove the four bolts, lockwashers, and flat washers
securing the valve to the bracket and the steering col-
umn. Remove the control valve, leaving the steering col-
umn in the cab.
Installation
1. Position the control valve to the bracket and steering col-
umn and install the four flat washers, lockwashers, and
bolts. Torque bolts; refer to Fasteners and Torque Val-
ues, page 1-15 for proper torque value.
2. Connect the five hydraulic hoses to the control valve as
tagged during removal.
3. Start the engine and check for proper operation and any
leakage.
Rear Steer/ Axle Lockout/Fan Drive Valve
Description
The rear steer valve/axle lockout/fan drive directionally
controls the outrigger circuit, outrigger pin circuit, and the
rear steer circuit. The valve is mounted on the front face of
the carrier frame member forward of the swivel.
The valve is made up of three sections. The inlet section
contains a solenoid valve and a 2000 psi (13.8 MPa) relief
valve. The relief valve is the main relief for both systems. The
solenoid valve is normally open, bypassing oil to the
reservoir. Operation of either system energizes the solenoid
valve to close it and route oil to the applicable circuit.
The second section is the rear steer section and contains a
three position four-way solenoid valve. The solenoid valve is
controlled by the rear steer switch in the operator’s cab. A
bolt on manifold that contains work port double pilot operated
check valves.
The third section is the outrigger section and contains two
bolt-on three position four-way solenoid valves, a bolt on
manifold that contains work port double pilot operated check
valves with integral 300 psi (2.1 MPa) rod side and 3000 psi
(20 MPa) piston side thermal relief valves. The solenoid
valve is controlled by the extend/retract switch in the
operator’s cab.
The second and third sections both contain a double pilot
operated check valve.
Maintenance
Removal
1. Tag and disconnect the electrical connectors to the rear
steer/axle lockout/fan drive valve.
2. Tag and disconnect the hydraulic lines to the rear steer/
axle lockout/fan drive valve. Cap or plug the lines and
ports.
3. Remove the four bolts and nuts securing the rear steer/
axle lockout/fan drive valve to the crane. Remove the
valve as a complete assembly.
Installation
1. Position the rear steer/axle lockout/fan drive valve on its
mount. Secure the valve with the four nuts and bolts.
2. Connect the hydraulic lines to the rear steer/axle lock-
out/fan drive valve as tagged during removal.
3. Connect the electrical connectors to the rear steer/axle
lockout/fan drive valve as tagged during removal.
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