Section 16: SUSPENSION
PA1593
15
a) Jack vehicle until the tire clears the
ground, and place safety supports
underneath body.
CAUTION
Only the recommended jacking points must be
used as outlined in Section 18, “Body”.
b) Support the axle with a suitable hydraulic
floor jack at the recommended jacking
point.
c) Remove wheel.
2. Exhaust compressed air from accessory air
tank by opening drain cock under reservoir.
3. Disconnect the height control valve link and
pull down the overtravel lever to ensure all
air is exhausted from air springs.
NOTE
While performing this step, do not change the
height control valve overtravel lever
adjustment.
4. Disconnect air line from air spring, remove
elbow (if applicable), and cover both the line
end and fitting to prevent the entry of foreign
matter.
5. Remove the air spring upper nut, and then
the two lower nuts. Remove air spring.
3.1.3 Installation
1. Compress air spring as necessary, then
aligning studs with their holes, position air
spring between both the lower and upper
supports. Thread the lower nuts and the
small upper nut a few turns.
NOTE
To facilitate air spring installation, compress it
manually then put a piece of tape over the air
line threaded fitting. This prevents air from
getting back into the bag and keeps it
compressed, thus enabling to place the bag in
between the mounting plates and greatly
easing installation.
2. Tighten and torque the lower stud nuts, and
then the upper one to 20–25 lbf-ft (27–34
Nm).
3. Screw on the remaining upper nut (large
nut) and tighten to 20–25 lbf-ft (27–34 Nm).
4. Install elbow (if applicable), then connect air
line.
5. Connect the height control valve link.
6. Build up air pressure in system.
NOTE
To accelerate this operation, air reservoirs can
be filled from an exterior air supply connected
to the accessory tank fill valve or to the
emergency fill valve.
7. Check operation of bellows, and with the
primary air system at normal operating
pressure (95 – 125 psi (655 – 860 kPa)),
coat the air line connections and air spring
mounting areas with a water and soap
solution. Bubbles will indicate an air leak,
and none is permissible. Repair or replace
defective parts.
8. Reinstall wheel.
9. Remove the hydraulic floor jack from under
the axle, then lower vehicle to ground.
3.2 SHOCK ABSORBERS
Double-action, telescoping-type shock
absorbers ensure a smooth ride and enhance
vehicle stability on the road. All shock absorbers
are eye-type mountings. The tag axle is
provided with two shock absorbers while the
drive axle is provided with four of them (Fig. 13,
14 and 16).
Shock absorbers are non-adjustable and non-
repairable. Maintenance requirements involve
replacement of the rubber mounting bushings,
and tightening of all shock absorber pins at the
proper torque of 500 - 550 lbf-ft (680 - 750 Nm)
when shock absorber replacement occurs. If a
shock absorber becomes inoperative, complete
unit must be replaced.
CAUTION
When a shock absorber is found defective,
always replace with a new set on affected
axle, except if there has been a recent
replacement of one unit. The following method
will help in determining if both shock
absorbers on the same axle have to be
replaced.
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