Chevrolet Light Duty Truck 1973 Service Manual page 179

rigid axle and one of them passes over a bump the axle
executes an angular movement in the (front view)
vertical plane and both of the wheels perform
movements of the same angular magnitude. With
independent suspension the movement of the two wheels
are not interdependent; one wheel does not force the
other wheel to deflect.
W ith the independent suspension, the steering knuckle
and wheel spindle are connected to the vehicle through
ball joints and control arms.
Steering Knuckle and Wheel Spindle
The wheel spindle is the unit that carries the hub and
bearing assembly with the aid of the knuckle assembly.
The hub assembly has also become the brake disc
assembly.
As pointed out under conventional and independent
suspensions, the wheel spindle is connected to the vehicle
through a steering knuckle and ball joints.
The spindle carries the entire wheel load. In order to
reduce friction, on the sprindle and wheel hub, wheel
bearings are provided. The design and placement of
these bearings on the spindle is such that the center
plane of the wheel is closer to the center plane of the
wheel is closer to the center plane of the inner bearing
than the outer bearing. The reason for this is to bring
the wheel as close as possible to the knuckle axis. For this
same reason the inner bearing will usually be larger than
the outer bearing. Wheel bearing service is covered in
detail elsewhere in this section.
Coil Spring
Coil springs are just what their name implies. They are
coils of steel wire. A coil spring can be installed on the
front suspension or rear suspension of a vehicle with the
method of attachment varying to suit the application.
On the front suspension the lower control arm provides
the seat for the coil spring with the upper end housed
within the frame crossmember. The function of the coil
spring is the same as the leaf spring, that is, to cushion
shock imparted to the wheel by road roughness or
obstacles.
Since a coil spring provides little directional stability
control arms are provided and connect between the
vehicles frame and axle assembly.
Shock absorbers are used with the springs and are
covered elsewhere in this section.
CONTROL ARMS
(Independent Suspension)
The front control arms are said to be the SLA type
(Short and Long Arm). The control arms attach to the
vehicle with bolts at their inner pivot points and to the
steering knuckle (which is part of the front wheel
spindle) at their outer points. The outer attachment is
made through ball joints secured to the control arms and
FRONT S U S PEN SIO N
bolted to the steering knuckle. This arrangement allows
the front wheel suspension to move up and down with
respect to the vehicle frame (spring action) and swing at
various angles for vehicle steering.
Control Arm Bushings
Two different types of bushings are used in 1973
independent suspension trucks. G-10 and 20 series and
C-10 series trucks use new rubber bushings for both
upper and lower control arms. All P series, C-20/30 and
G-30 use steel bushed upper and lower control arms. The
rubber bushings provide a better more enjoyable ride,
while the steel bushings are needed for heavy duty
applications.
BALL JOINTS (Fig. 5)
Ball joints are used to connect the control arms to the
steering knuckle. The upper ball joint is usually riveted
to the control arm and connects to the steering knuckle
through a tapered stud that is held in position with a
castellated nut and a cotter pin. The lower ball joint is
usually pressed into the control arm and connects to the
steering knuckle through a tapered stud that is held in
position with a castellated nut and a cotter pin.
A ball joint stud, nut and rubber seal is about all your
eye will see of the ball joint assembly. The function of
the rubber seal is to retain the lubricating grease, which
it contains, and to protect this grease from contam ina­
tion by water or foreign material (sand, dirt, etc.). If this
seal is damaged (torn or pulled off its metal retainer) the
ball joint should be replaced. Check the Service
procedure for inspection and replacement of a ball joint
suspected of being in need of replacement.
NOTE: Grease fittings on ball joints should
be wiped clean before applying grease to the
joint.
SHOCK ABSORBERS
Shock absorbers are hydraulic devices that help to
control the up-and-down and rolling motion of a vehicle
SHORT ARM
Fig. 4—Control Arms
3-5
BALL JOINT
LIGHT DUTY TRUCK SERVICE MANUAL