Chevrolet 70 1969 Series, Shop Manual

Page: 468 / 913

STEERING SYSTEM 9B-17
SECTION 9B
POWER STEERING
GENERAL
The power steering system provides automatic
hydraulic assistance to the turning effort applied
to the mechanical steering system.
On all models, except those equipped with the
F-160 front axle, the power steering system con­
sists of a control valve, power cylinder and a hy­
draulic pump used in conjunction with the steering
gear.
A typical power steering system used on con­
ventional cab models is shown in Figure 1 and a
power steering system used on Series 80 tilt cab
models is shown in Figure 2.
N O T E : On Series 70 tilt cab models, a con­
necting rod is used between the Pitman arm and
left steering arm and an axle mounted power cyl­
inder is used.
On all models equipped with the F-160 front
axle, the power steering system consists of a con­
trol valve, hydraulic pump, and two side mounted
power cylinders. The left-hand cylinder socket is
attached to the Pitman arm and the right-hand cyl­
inder socket is attached to an idler arm.
Figure 1 — Power Steering System (Conv. Cab Modell ITypicalI
The power steering system is a complete in­
line unit. The steering shaft, hydraulic valve,
worm, and ball nut are in a line, making a com ­
pact, space-saving steering gear. The recirculat­
ing ball type mechanical steering gear is used in
conjunction with the control valve.
The power steering will not operate without
driver guidance; therefore when turning effort is
relieved, the front wheels return to neutral or
straight ahead position.
On all models except those equipped with the
F-160 front axle, the power cylinder is actuated
by operation of the control valve which supplies
hydraulic fluid to either side of the power cylinder
piston as required, depending on the position of the
valve. The pressure used to operate this system
is supplied by either a vane-type or slipper-type
oil pump.
On vehicles equipped with the F-160 front
axle, the power cylinder is actuated by operation
of the control valve which supplies hydraulic pres­
sure to a junction block which in turn supplies
hydraulic fluid to the right and left power cylinders
as required, depending on the position of the valve.
The pressure used to supply this system is sup­
plied by a vane-type oil pump which is belt driven
from the engine crankshaft pulley in conjunction
with other accessories.
If for any reason the power steering system
should fail, the control valve "locks up" and the
steering gear operates manually, giving the driver
full control of the vehicle. Response of the steer­
ing gear in effort applied to the steering wheel has
been greatly increased. This fast response gives
the driver greater control of the vehicle.
MAINTENANCE
The power steering system requires little
maintenance. However, the hydraulic system should
be kept clean to insure maximum operating per­
formance and trouble-free service. Periodic in­
spection to check for leaks should also be made.
At regular intervals the pump hydraulic fluid
level in the reservoir should be checked and fluid
added when required. Refer to LUBR ICA TION (SEC.
0) for type of fluid to be used, method, and inter­
vals for filling.
On all hydraulic pump models, the fluid reser­
voir either encases the pump or is mounted on top
of the pump. An additional reservoir is mounted on
a bracket attached to the radiator support on con­
C H E V R O lEr SERIES 7 0 - 8 0 H E A V Y D U T Y T R U C K S H O P M A N U A L