Chevrolet 1977 light duty truck Service Manual page 285

problem still exists (poor handling, bottoming, noise,
ride sway, etc.), proceed.
Inspecting and Testing the Shocks
T hree procedures are included in this step. Thet are
(a) Bounce Test, (b) Inspecting Shock M ountings for
Noise (Looseness) and (c) M anually O perating Shocks to
D eterm ine if Shocks are Weak, Leaking Hydraulic Fluid,
a n d / o r if Shocks have an Internal Noise Condition.
IM PORTANT: Test procedures (b) and (c)
require vehicle to be on a hoist that supports
wheels or rear axle housing and front lower
control arms.
Bounce Test
N OTE: This is only a com parison type test to help
locate the suspected
before proceeding.
Test each front and rear shock by bouncing each
corner o f the vehicle. This can usually be done by lifting
up and pushing down on the end of the bum per near
each corner o f the vehicle until m axim um movement up
and down is reached. Then let go o f bum per and observe
if the up and down motion stops very quickly. II' up and
down motion continues longer at one corner when
c om pared to opposite corner
shocks), the one having the longer up and down motion
m ay be suspect. Do Not
com plaint is noise, this test should help to locate the
suspected area.
Inspecting Shock Mountings
If noisy a n d / o r loose
suspected, place vehicle on hoist that supports wheels and
check all mountings for the following conditions:
(1) W orn or defective gromm ets
(2) Loose m ounting nuts
(3) Possible interference condition
(4) Bump stops missing
If no a p p a re n t 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
an d (2) M anually O perating Shock. It should aid the
technician to localize defective shocks caused by internal
noise in the shock, weak, leaking, etc.
1. Inspecting
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 3C-8).
Certain precautions should be observed when
inspecting shocks for leaks:
shock or noise condition
(example, both front
com pare front to rear. If
shock m ountings
Shocks for Possible Loss
• shocks m ay have glossy paint on them. Do
not confuse this paint with a leak condition.
• a slight trace o f shock fluid around the seal
cover area is
shock seal is engineered
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
N OTE: It may be necessary with certain types o f
shock mountings to fabricate a bracket that can be
installed on a shock to enable a technician to
securely grip the shock w hen manually operating
the shock. See Figure 3C-9 for suggested methods
of providing tem porary grip.
This test should help the mechanic to isolate the
following shock defects:
• binding condition internally
• verify leaking shock
• im proper or defective valving
(a) If suspected problem
disconnect both front shock lower mountings and stroke
each shock as follows: G rip the lower end o f the shock
securely and pull down (rebound stroke) then push up
(compression stroke). The control arms will limit the
movement o f the front shocks during the compression
are
stroke. Com pare the rebound resistance between both
front shocks, then com pare the compression resistance. If
a noticeable difference can be felt during either stroke,
usually the shock having the least resistance is at fault.
(b) If shock has an internal noise condition,
of
not cause for replacement. The
to perm it a slight
is in front shocks,