Shock A B S O Rb E - GMC 1986 P-Truck Service Manual

3C-40 FRONT SUSPENSION
Tighten
• Nut (115) to 68 N m (50 ft. lbs.).
5. Shock absorber (113) to the axle (157) (figure 34).
• Washer (111) and nut (109).
Tighten
• Nut (109) to 50 N m (37 ft. lbs.).
FOUR WHEEL DRIVE FRONT SUSPENSION
SHOCK ABSORBER
□ Remove or Disconnect (Figures 37 through 39)
• Raise the vehicle on a hoist.
1. Shock absorber (220) from the frame.
• Nut (212), washer (213) and bolt (219) (figure
36).
2. Shock absorber (220) from the axle.
• Nut (212), washer (213) and bolt (225).
• Quad shocks (RPO Z75) have a spacer
(246) between them (figure 39).
BENCH TEST: SPIRAL GROOVE SHOCK
ABSORBERS
1. Purge the air from the pressure chamber.
• Extend the shock vertically—top end up.
• Turn the sh ock over and c o lla p se it
vertically—top end down.
• Repeat the above step five times.
2. Place the shock absorber in a vise with the jaws
clamped onto the shock's bottom mount.
— Shock absorber should be positioned
vertically in the vise—top end up.
— Do not clamp the vise jaws on the shock's
reservoir tube.
3. Pump the shock absorber at various rates of
speed and observe the rebound force.
— Rebound force is normally stronger than the
compression force (approximately two to
one).
— Rebound force should be smooth and
constant for each stroke rate.
4. Compare with a good shock absorber.
5. If one of the following are observed, replace the
shock absorber.
— A skip or lag at reversal near mid-stroke.
— A seize (except at the extreme ends of
travel).
— A noise (grunt or squeal) after completing
one full stroke in both directions.
— A clicking noise at fast reversal.
ON-VEHICLE SERVICE:
6. Wheel and tire assembly. Lower the vehicle to the
ground.
7. Check the front end alignment.
• Refer to FRONT END ALIGNMENT (SEC.
3B1).
BENCH TEST: NON-SPIRAL GROOVE RESERVOIR
SHOCK ABSORBERS
• P urging air from non-spiral groove shock
absorbers is not necessary. The shock absorbers
have a gas filled cell in their reservoirs (as
opposed to the air filled cell in the spiral groove
shock absorber reservoirs).
1. Place the shock absorber in a vise with the jaws
clamped on the shock absorber's top mount.
— Shock absorber should be held vertically in
the vise with its bottom end up.
— Do not clamp the vise jaws on the shock's
reservoir tube.
2. Pump the shock absorber at various rates of
speed and observe the rebound force.
— Rebound force is normally stronger than the
compression force (approximately two to one).
— Rebound force should be smooth and constant
for each stroke rate.
3. Compare with a good shock absorber.
4. If one of the following are observed, replace the
shock absorber.
— A skip or lag at reversal near mid-stroke.
— A seize (except at the extreme ends of
travel).
— A noise (grunt or squeal) after completing
one full stroke in both directions.
— A clicking noise at fast reversal.
Install or Connect (Figures 37 and 38)
NOTICE: For steps 1 and 2, refer to the
"Notice" on page 3C#7.
1. Shock absorber (220) to the axle.
• Bolt (225), washer (213), and nut (212).
• Spacer (246) must be positioned between
the shock absorbers (220) on vehicles with
quad shocks, RPO Z75 (figure 39).