Chevrolet Light Duty Truck 1973 Service Manual page 206

3 -3 2 FRONT SU SPEN SION
bracket that can be installed on a shock to
enable a technician to securely grip the shock
when manually operating the shock. See
Figure 45 for suggested methods of providing
temporary grip.
This test should help the mechanic to isolate the
following shock defects:
• loose piston
• binding condition internally
• verify leaking shock
• improper or defective valving
(a) If suspected problem is in front shocks,
disconnect both front shock lower mountings
and stroke each shock as follows: Grip the
lower end of the shock securely and pull down
(rebound stroke) then push up (compression
stroke). The control arms will limit the
movement of the front shocks during the
compression stroke. Compare the rebound
resistance between both front shocks, then
compare 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, extend
shock fully, then exert an extra pull. If a small
additional movement is felt, a loose piston is
indicated and shock should be replaced. Other
noise conditions that require shock replace­
ment are:
• a grunt or squeal after one full stroke in both
directions
• a clicking noise on fast reverse
• a skip or lag at reversal near mid-stroke
When air adjustable shocks
IM PORTANT:
are being manually operated, the air line
must be disconnected at the shock absorber.
BENCH CHECKS
The bench checks are recommended if the proper type
hoist is not available to perform the "on car" tests, or if
there is still some doubt as to whether the shocks are
defective. In addition, the bench test allows a more
thorough visual inspection.
Bench check procedures are discussed for three general
types of shocks.
SPIRAL GROOVE RESERVOIR
If this type of shock has been
IMPORTANT:
stored or allowed to lay in a horizontal
position for any length of time, an air void
will develop in the pressure chamber of the
shock absorber. This air void if not purged,
can cause a technician to diagnose the shock
as defective. To purge the air from the
pressure chamber, proceed as follows: (Refer
to figure 46)
(a) Holding the shock in its normal vertical position
(top end up), fully extend shock.
(b) Hold the top end of the shock
collapse the shock.
(c) Repeat Steps (a) and (b) at least five (5) times to
assure air is purged.
Bench Test Procedure
1. This is a comparison type test. If possible, obtain a
new or known good shock with same part number
as shock under test.
2. With shocks in vertical position (top end up), clamp
bottom mounts in vise.
Do not clamp on reservoir tube or
CAUTION:
mounting threads.
and fully
down
LIGHT DUTY TRUCK SERVICE MANUAL