Chevrolet 1977 light duty truck, Руководство по обслуживанию

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p ro b lem 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 an u ally O perating Shocks to
D eterm in e if Shocks are Weak, Leaking Hydraulic Fluid,
a n d / o r if Shocks have an Internal Noise Condition.
IM PO RTANT: Test procedures (b) and (c)
require vehicle to be on a hoist that supports
wheels or re a r axle housing and front lower
control arms.
Bounce Test
N O T E : This is only a com parison type test to help
locate the suspected shock or noise condition
before proceeding.
Test each front and rear shock by bouncing each
corner o f the vehicle. This can usually be done by lifting
up an d push in g down on the end o f the b um per near
each corner o f the vehicle until m ax im u m movem ent up
and down is reached. Then let go o f b u m p er and observe
if the up and down motion stops very quickly. II' up and
down motion continues longer at one corner when
c o m p a re d to opposite corner (example, both front
shocks), the one hav in g the longer up and down m otion
m ay be suspect.
Do Not com pare front to rear. If
co m p lain t is noise, this test should help to locate the
suspected area.
Inspecting Shock Mountings
If noisy a n d / o r loose shock m o u n tin g s are
suspected, place vehicle on hoist th at supports wheels and
check all m ountings for the following conditions:
(1) W orn or defective grom m ets
(2) Loose m ounting nuts
(3) Possible inte rference 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 o f Hydraulic Fluid
an d (2) M anually O p e ra tin g 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 o dor an d dark brown tint (Figure 3C-8).
Certain precautions should be observed w hen
inspecting shocks for leaks:
• shocks m ay have glossy p ain t on them. Do
not confuse this pain t with a leak condition.
• a slight trace o f shock fluid a ro u n d the seal
cover area is
not
cause for replacement. The
shock seal is engineered to perm it a slight
seepage to lubricate the rod. The shock absorber
has reserve fluid to com pensate 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 m anually operate shock as described in Step
(2). Fluid will reap p ear if shock is leaking.
2. Manually Operating Shocks
N O TE: It m ay be necessary with certain types o f
shock m ountings to fabricate a bracket that can be
installed on a shock to enable a technician to
securely grip the shock w hen m anually operating
the shock. See Figure 3C-9 for suggested methods
o f providing tem p o rary 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 is in front shocks,
disconnect both fro n t shock lower m ountings and stroke
each shock as follows: G r ip 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
stroke. C om p are the rebound resistance between both
front shocks, then c o m p are 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,