Chevrolet Light Duty Truck 1973 Service Manual page 207

TYPICAL FRONT SHOCK
BOTTOM
M OUNT \
ROD EXTENDED
(REBOUND) s.
SHOCK
COLLAPSED
BOTTOM
TOP END
M OUNT
DOWN
INVERT
TH EN C OLLAPSE
Fig. 46—Position for Purging Air From Shocks
3. Manually pump each shock by hand at various
rates of speed and compare resistance of suspected
shock with the new one.
NOTE: Rebound resistance (extending the
shock) is normally stronger than the compres­
sion resistance (approximately 2:1). However,
resistance should be smooth and constant for
each stroking rate.
4. Observe or listen for the following conditions that
will indicate a defective shock:
• a skip or lag when reversing stroke at mid travel.
• seizing or binding condition except at extreme
end of either stroke.
• a noise, such as a grunt or squeal, after
completing one full stroke in both directions.
• a clicking type noise at fast reversal.
• fluid leakage.
5. To check for a loose piston, completely extend
shock to full rebound; then exert an extra hard pull.
If a give is felt, a loose piston is indicated and
shock should be replaced.
PLIACELL OR GENETRON
Pliacell and Genetron are some of the trade names used
to indicate a gas-filled cell in the shock reservoir. The
reservoirs of Pliacell and Genetron shocks are smooth,
compared to the spiral groove type. The cell takes the
place of air in the reservoir. Thus, aeration or foaming
of the fluid is eliminated, as air and fluid cannot mix.
Due to this feature, these shocks should be bench
checked in an
inverted position
stroked, a lag is noticed, it means the gas-filled cell has
been ruptured, and the shock should be replaced. If no
lag is noticed, the remainder of the bench check is the
same as given in the Spiral Groove Reservoir, Section 1,
Bench Check Procedure.
TYPICAL REAR SHOCK
- U r
BOTTOM
M OUN T
SHOCK -
ROD EXTENDED COLLAPSED
(REBOUND) '
BOnOM
• I I
TOP END
m o u n t , ^ mrrg
VlUUli I \ I
DOWN
INVERT. TH E N C OLLA PS E
(top end down). If, when
FRONT SU S PEN SIO N
AIR ADJUSTABLE SHOCKS
This type of shock contains an air chamber like the
spiral groove reservoir type, and must have the air
purged from the working chamber. See Section 1, Spiral
Groove Reservoir. After air has been purged from shock,
proceed as follows:
(a) Clamp lower shock mounting ring in vise in
vertical position with larger diameter tube at the
top.
(b) Pump unit by hand at different rates of speed.
Smooth resistance should be felt through the
length of the stroke. Since the units are normally
pressurized, the sound of air bubbles or a gurgling
noise is
normal.
(c) The rem ainder of the bench check is the same as
given in the Spiral Groove Reservoir, Section 1,
Bench Check Procedure.
BEARINGS AND RACES
BENCH DIAGNOSTIC PROCEDURE
This section describes common types of bearing distress
and their causes. Illustrations are included to help
diagnose the cause of distress and comments are
provided to help make effective repairs.
Consider The Following Factors When
Diagnosing Bearing Distress:
1. Note General Condition of all parts during
teardown and examinations.
2. Classify the failure with the aid of these
illustrations where possible.
3. Determine the cause. Recognizing the cause will
permit correction of the problem and prevent a
repeat failure of the same type.
4. Make all repairs
procedures.
Common Causes For Bearing Distress
Includes The Following:
1. Improper adjustment or preloading.
2. Mounting or teardown abuse.
3. Improper mounting methods.
4. Inadequate or wrong lubricants.
5. Entrance of dirt or water.
. W ear from dirt or metal chips.
6
7. Corrosion or rusting.
. Seizing or smearing from overload.
8
9. Overheating causing tempering.
10. Frettage of bearing seats.
11. Brinelling from impact loads and shipping.
12. M anufacturing defects.
13. Fatigue pitting and spalling.
3 -3 3
following recommended
LIGHT DUTY TRUCK SERVICE MANUAL