GMC PD-4103 Maintenance Manual page 188

Sec. 15
Page 168
GM COACH MAINTENANCE MANUAL
SPRING SUSPENSION
Figure 4-Removing Shock Absorber End Cap
hole. Replace filler plug and move shock absorber
arm up and down to work fluid into piston cyl-
inders; then add enough fluid to fill reservoir. To
provide necessary air space, allow fluid to escape
down to lower edge of filler plug hole before· re-
placing plug. If leaks are evident around end
caps, valve plugs, or filler plug, replace gaskets.
Packing washers on shock absorbers which
have been operating with fluid below proper level
may become worn, causing leaks around shaft.
This necessitates replacement of shock absorber.
REPLACEMENT
While shock absorber can be removed with
wheel in place, removal of wheel will make shock
absorber more accessible. Disconnect link from
shock absorber arm. Disconnect unit from frame
side rail, and remove from vehicle.
To install shock absorber, reverse removal
procedures. Tighten link stud nuts to torque list-
ed in "Specifications" at end of this section.
Figure 5-lnstal/ing Valve Spring Retainer
SHOCK ABSORBER OVERHAUL
If shock absorber body or arm is broken, arm
is "frozen," absorber leaks at arm, or there is no
resistance in unit when arm is moved and unit is
full of fluid, shock absorber should be overhauled.
DISASSEMBLY (Fig. 3)
1. Remove dirt, grease, and loose paint from
exterior.
2. Remove unit from vehicle and place in vise,
being careful to clamp vise so as not to cause a
bind on pistons.
3. Remove filler plug, drain fluid completely;
then remove end caps with special tool (J-767) as
shown in figure 4.
4. Remove relief valve nuts (8 and 13), re-
bound valve (10), compression valve (11), and in-
take valves (17). To remove intake valves, first
remove valve spring retainer clip (15) with a screw
driver; then lift out springs (16) and valves.
5. Remove plugs (20) over piston screws (19);
then disassemble pistons (13 and 18) by removing
piston screws (4) and remove from cylinder.
6. Wash all parts in kerosene; then inspect
for wear. Clean valve orifices with compressed
air.
7. Check camshaft for wear in housing by
moving shock absorber arm sideways. If shaft is
galled or worn, replace complete shock absorber.
ASSEMBLY (Fig. 3)
1. Assemble pistons in cylinder, keeping the
cam clearance in pistons up.
2. Tighten piston screws firmly, then back
off one to one and a half turns to prevent binding
between cam (19) and cam buttons (7); then in-
stall new plugs (20) over piston screws.
3. Replace intake valves (17), springs (16),
and valve spring retainer clips (15), using special
tool
(J
-896-A) as shown in figure 5.
4. Install rebound valve (10), spring (9), and
valve nut (8). Install compression valve (11),
spring (12), and valve nut (13). Use new gaskets.
5. Install one end cap (5) using new gasket ;
then rotate unit and fill to capacity with fluid.
While filling, move arm to expel air from fluid.
6. Install other end cap; then fill unit as pre-
viously directed under "Filling" in this section.
NOTE: Shock absorber body, arm,
packing gland, camshaft, and cam are not
replaceable due to special fixtures and
presses required to assemble and disas-
semble these parts.
SHOCK ABSORBER LINKS
Links are used between shock absorber arm
and axle as shown in figure 1. Unsatisfactory
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