SECTION 16: SUSPENSION
14
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Section 16 revised April 2019)
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 according to Torque
Table under heading Torque Specifications.
3. Screw on the remaining upper nut (large
nut) and tighten according to Torque Table
under heading Torque Specifications.
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, 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 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 (Figure 12 & Figure
13).
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.
3.2.1
Inspection
Loosen lower mounting of both shocks, and then
carefully attempt to raise and lower the bottom
portion of each shock. Note the rate of effort for
distance of travel. Replace both shocks if a
definite differential rate is found.
The shock must be bench checked in an upright,
vertical position. If checked in any other position,
air will enter the cylinder tube and make the
shock absorber appear defective.
Proceed as follows to check shock absorbers:
1. With the shock absorber in a vertical
position (top end up), clamp the bottom
mount in a vise.
CAUTION
Do not clamp the reservoir tube or the dust
tube.
2. Rotate the dust tube. Notice any binding
condition (may be compared with new unit).
Binding condition indicates a scored rod.
Units with scored rods should be replaced.
3. Fully extend shocks and check for leaks in
the seal cover area. Shock fluid is a very
thin hydraulic fluid that has a characteristic
odor and dark brown tint. A slight trace of
shock fluid around the seal cover area is not
a cause for replacement. The shock seal is
designed to permit a very slight seepage to
lubricate the rod. Units that leak should be
replaced.
4. Visually check shock for dents that could
cause the shock to bind. Also, check for a
bent rod.
