Chevrolet Light Duty Truck 1973 Service Manual page 205

SHOCK ABSORBER
DIAGNOSIS
ON VEHICLE CHECKS
(Follow the Procedures Outlined Below in the Order
Indicated).
Preliminary Inspection and Ride Test:
Tire Pressure
Check tire pressure compare to vehicle specifications and
adjust as required. Poor vehicle control and ride
complaints are caused in many cases by improper tire
inflation.
Special Suspension Equipment
Check Service Parts Identification Sticker for any special
suspension equipment; such as, a heavy duty suspension.
Vehicles equipped with this type of option have a
somewhat stiffer or harsh ride, and this should be kept in
mind during the following tests. If complaint about
stiffness should occur while vehicle is still new (under
5,000 miles), owner should be advised to have ride
rechecked after 7,000 to 8,000 miles.
Vehicle Load Conditions
Note any exceptional load conditions under which the
owner normally operates the vehicle; such as, large tool
boxes full of tools, pick up bed full etc. If exceptional
loading is apparent, check the distribution of this weight.
Note if it is all toward one side of the vehicle or at the
extreme rear of the vehicle. Reposition load as required
to obtain a more uniform weight distribution.
Check Vehicle Ride and Handling
After completing previous checks, ride vehicle with
owner to determine if problem has been corrected or to
definitely establish type of problem that still exists. If
problem still exists (poor handling, bottoming, noise,
ride sway, etc.), proceed.
Inspecting and Testing the Shocks
Three procedures are included in this step. Thet are (a)
Bounce Test, (b) Inspecting Shock Mountings for Noise
(Looseness) and (c) Manually Operating Shocks to
Determine if Shocks are Weak, Leaking Hydraulic Fluid,
and/or if Shocks have an Internal Noise Condition.
Test procedures (b) and (c)
IMPORTANT:
require vehicle to be on a hoist that supports
wheels or rear axle housing and front lower
control arms.
Bounce Test
NOTE: This is only a comparison type test to
help locate the suspected shock or noise
condition before proceeding.
Test each front and rear shock by bouncing each corner
of the vehicle. This can usually be done by lifting up and
pushing down on the end of the bumper near each
corner of the vehicle until maximum movement up and
down is reached. Then let go of bumper and observe if
FRONT SU S PEN SIO N
the up and down motion stops very quickly. If up and
down motion continues longer at one corner when
compared to opposite corner (example, both front
shocks), the one having the longer up and down motion
may be suspect.
Do Not
complaint is noise, this test should help to locate the
suspected area.
Inspecting Shock Mountings
If noisy and/or loose shock mountings are suspected,
place vehicle on hoist that supports wheels and check all
mountings for the following conditions:
(1) Worn or defective grommets
(2) Loose mounting nuts
(3) Possible interference condition
(4) Bump stops missing
If no apparent defects are noted in this step but noise
condition still exists when vehicle is bounced up and
down, proceed.
Inspecting Shocks for Leaks and
Manually Operating Shocks
This procedure is sub-divided into two general areas, (1)
Inspecting Shocks for Loss of Hydraulic Fluid and (2)
Manually Operating Shock. It should aid the technician
to localize defective shocks caused by internal noise in
the shock, weak, leaking, etc.
1. Inspecting Shocks for Possible Loss of Hydraulic
Fluid.
(a) Disconnect each shock lower mounting as
required and pull down on the shock until it is
fully extended.
(b) Inspect shocks for leaks in seal cover area.
Shock fluid is a very thin hydraulic fluid and
has a characteristic odor and dark brown tint
(Figure 44).
Certain precautions should be observed when
inspecting shocks for leaks:
• shocks may have glossy paint on them. Do
not confuse this paint with a leak condition.
• a slight trace of shock fluid around the seal
cover area is
not
shock seal is engineered to permit a slight
seepage to lubricate the rod. The shock
absorber has reserve fluid to compensate for
the slight seepage.
• shocks are sometimes incorrectly diagnosed
as leakers due to oil spray originating from
some other source. If in doubt, wipe the wet
area from and manually operate shock as
described in Step (2). Fluid will reappear if
shock is leaking.
2.
Manually Operating Shocks.
NOTE: It may be necessary with certain
types of shock mountings to fabricate a
3-31
compare front to rear. If
cause for replacement. The
LIGHT DUTY TRUCK SERVICE MANUAL