THEORY OF OPERATION - CONTINUED
STEERING SYSTEM - CONTINUED
System Description. When the steering wheel is turned, the worm in the gear nut moves. One end of control arm is in a
groove near the bottom of the worm shaft. The worm moves the control arm, which in turn moves the valve spool into
turn position RIGHT or LEFT. The oil from the pump is routed by the steering control valve to the rod end of one steer-
ing cylinder and the head end of the opposite steering cylinder, causing the machine to articulate. As the steering cylin-
ders turn the machine, the rod is moved out of the follow-up cylinder (sender). This movement of the piston sends oil to
the rod end of follow-up cylinder (receiver). The operator stops turning the steering wheel when the machine is at the
amount of turn desired. When movement of steering wheel is stopped, the worm also stops turning. The moving steering
cylinders and follow-up cylinders do not stop until the steering control arm moves gear the sector, which moves gear nut
and worm down. When the worm shaft is moved down, steering control on the end of the worm shaft moves valve spool
to the HOLD position. This stops the flow of pump oil to the steering cylinders, and the machine stops articulation at the
amount of turn desired.
Follow-Up Cylinder (Sender). Sends signal pressure feedback to the follow-up cylinder (receiver). This cylinder
is mounted on the left side of the articulation steering arms.
Bleed Valves. Used for removal of air from the follow-up cylinders. Located at rod end of follow-up cylinder
Relief Valve. Prevents over pressurization
of rod end
of follow-up cylinder. Located
on rod end
of follow-up cyl-
Follow-up Cylinder Receiver. Receives feedback hydraulic pressure from the follow-up cylinder (sender). This
cylinder is located beneath the floor plate of the operator compartment.
Diverter Valve. Mounted on the supplemental steering pump. Acts as a flow control valve. When the machine
ground speed is above 15 mph (approximately), output hydraulic fluid from the large section of supplemental
steering pump is redirected back to the input of the pump. Below 15 mph (approximately), the output from both
pump sections, large and small, is directed into the steering control valve.
Gear Sector. Mounted
in the steering gearbox
at the lower end
of the steering column. This gear receives move-
ment from the gear nut via the worm and transmits action to the steering control arm.
Worm. Part of the steering column assembly. Mounted in the steering gearbox, it receives turning motion from the
Part of the steering gearbox. This gear nut rides
on the worm, transferring rotary motion (steering wheel
turning) into lever movement. The gear nut works with the gear sector to move the steering control arm.
Steering Control Arm. Connected to the output lever on the steering gear box, and to the follow-up cylinder
(receiver). This control arm is used on the servo-feedback for steering.
Steering Control. Connected to an arm that is indexed on the lower portion of the steering worm shaft. When the
steering wheel is rotated left or right, the worm shaft moves slightly up or down. This movement is transmitted
through the arm to the control arm, which is connected to the valve pool.
Check Valve. Allows oil from the supplemental steering pump to pass, but will not allow oil flow in a reverse
direction from the implement pump into the supplemental steering pump. In the event of supplemental steering
pump failure, the check valve seals off the supplemental steering pump system from the system hydraulics. Then,
only pump oil from the implement pump system is channeled to the steering system.
Steering Cylinder, Left Side. Receives hydraulic pressure for either extension or retraction. It causes the machine
to articulate left or right. This cylinder is mounted on the left side of the hitch and steering arrangement.
Relief Valve (Main). The system relief valve is mounted in the steering control valve. This valve prevents over
pressurization of the major components. It is set at 2,250 psi (15,513 kPa).