Chapter 9 Steering Systems 195
In operation, fluid pressure is directed to one side
of the piston and causes it to move outward or
inward, depending on which side of the piston is
being pressurized. This exerts pressure on the relay rod,
moving the linkage.
Control Valve
The control valve assembly is installed on the end
of the pitman arm, Figure 9-61. A ball socket from the
pitman arm is installed in the control valve. When the
pitman arm is moved, the ball socket moves a valve
contained in the control valve assembly. The valve then
directs pressurized fluid to the proper side of the power
cylinder.
Four-Wheel Steering
Some vehicles have four-wheel steering. In a four-
wheel steering system, the rear wheels can turn to assist
Left turn hole
Return oil
Pressure slot
Right turn hole
Return hole
Valve spool
Valve body
Return
slot
Body
Spool
Return oil
Body
Spool
Return oil
A B C
Figure 9-58. Action of the rotary valve showing oil flow and power rack-piston nut action. A—Straight ahead driving. B—Making a
right turn. C—Making a left turn. (General Motors)
Cross shaft
adjusting screw
Port sealing ball
Recirculating
ball guide
Power
piston
Left turn
power
chamber
Recirculating
ball guide
Right turn
power chamber
O-ring
Left turn
reaction ring
Left turn
reaction spring
Cylinder
head ferrule
Dowel
pin
Right turn
reaction spring
Right turn
reaction ring
Reaction
seal
Worm shaft
balancing
ring
Worm
shaft
Pivot lever
Oil inlet fitting
Linear control valve
Center thrust
bearing race
Cross shaft
Pump
Pump
drive belt
Power
cylinder
Center link
Control valve
Piston
rod
Booster
hoses
Pressure hose
Return hose
Figure 9-59. Cutaway view of a power steering gear that uses
a linear spool valve.(Chrysler)
Figure 9-60. A power steering system that uses a separate
power cylinder. (Moog)