the pinion shaft (spool valve) slightly. This action
moves the control valve and aligns the specific oil
passages. Pump pressure is then allowed to flow
through the control valve, the hydraulic line, and into
the power cylinder. Hydraulic pressure then acts on the
power piston and the piston action assists in pushing
the rack and front wheels for turning.
STEERING SYSTEM MAINTENANCE
Maintenance of the steering system consists of
regular inspection, lubrication, and adjusting
components to compensate for wear. When inspecting
the steering system, you will need someone to assist you
by turning the steering wheel back and forth through the
free play while you check the steering linkage and
connections. You will also be able to determine if the
steering mechanism is securely fastened to the frame. A
slight amount of free play may seem insignificant, but if
allowed to remain, the free play will quickly increase,
resulting in poor steering control.
After prolonged use, steering components can fail.
It is important that the steering system be kept in good
working condition for obvious safety reasons. It is
your job to find and correct any system malfunctions
quickly and properly
Steering Linkage Service
Any area containing a ball-and-socket joint is
subjected to extreme movements and dirt. The
combination of these two will cause the ball-
and-socket joint to wear. When your inspection finds
worn steering linkage components, they must be
replaced with new components. Two areas of concern
are the idler arm and the tie-rod ends.
IDLER ARM SERVICE.A worn idler arm
causes play in the steering wheel. The front wheels,
mostly the right wheel, can turn without causing
movement of the steering wheel. This is a very
common wear point in the steering linkage and should
be checked carefully.
To check an idler arm for wear, grab the outer end
of the arm (end opposite the frame) and force it up and
down by hand. Note the amount of movement at the
end of the arm and compare it to the manufacturers
specifications. Typically, an idler arm should NOT
move up and down more than 1/4 inch.
The replacement of a worn idler arm is as follows:
Separate the outer end of the arm from the center
link. A ball joint fork or puller can be used to force the
idler arms joint from the center link.
With the outer end removed from the center link,
unbolt and remove the idler arm from the frame.
Install the new idler arm in reverse order of
removal. Make sure that all fasteners are torqued to
manufacturers specifications. Install a new cotter pin
and bend it properly.
TIE-ROD END SERVICE.A worn tie-rod end
will also cause steering play. When movement is
detected between the ball stud and the socket,
replacement is necessary.
The replacement of a worn tie-rod end is as
Separate the tie rod from the steering knuckle or
center link. As with the idler arm, a ball joint fork or
puller can be used.
With the tie rod removed from the steering
knuckle or center link, measure tie-rod length. This will
allow you to set the new tie rod at about the same length
as the old one.
The alignment of the front wheel is altered
when the length of the tie rod is changed.
Loosen and unscrew the tie-rod adjustment
sleeve from the tie-rod end. Turn the new tie-rod end
into the adjustment sleeve until it is the exact length of
the old tie rod.
Install the tie-rod ball stud into the center link or
steering knuckle. Tighten the fasteners to
manufacturer's specifications. Install new cotter pins
and bend correctly. Tighten the adjustment sleeve and
check steering action.
Manual Steering System Service
Steering system service normally involves the
adjusting or replacement of worn parts. Service is
required when the worm shaft rotates back and forth
without normal pitman arm shaft movement. This
would indicate that there is play inside the gearbox. If
excess clearance is NOT corrected after the
adjustments, the steering gearbox must be replaced or
MANUAL GEARBOX ADJUSTMENT.
Since there are numerous steering gearbox
configurations, we will discuss the most common type,
recirculating ball and nut. There are two basic
adjustmentsworm bearing preload and over center