Section 16: SUPPLEMENT INFORMATION ON INDEPENDENT FRONT SUSPENSION (IFS)
16-29
FIGURE 23: TYPICAL AIR SPRING CLEARANCE
16058
FIGURE 24: FRONT HEIGHT CONTROL VALVE
16059
The appropriate vehicle body height is obtained
by measuring the clearance of all the air springs
installed on the vehicle. The two front air springs
clearance should be 11.7 inches (297.3 mm).
Refer to figure 23 to identify the correct area to
take measurement. The rear air springs clearance
should be 11.5 ± 0.25" (292 ± 6 mm) (refer to XL
Maintenance Manual, Section 16, paragraph "7.
SUSPENSION HEIGHT ADJUSTMENT" for rear
height control valves' adjustment). At this point, it
should not be necessary to make an adjustment
under normal service conditions. However, if an
adjustment is required, change the position of the
overtravel lever in relation to the overtravel control
body. The lever should be moved up to raise ve-
hicle height, and down to lower it. Check that main
air pressure is at normal operating pressure and
raise the vehicle to the specified height.
Caution:
Always adjust on "fill cycle". If it is neces-
sary to lower vehicle height, release sufficient air to be
well below height, and adjust to height or fill cycle.
The normal ride height is obtained by adjusting air
spring clearance of both front and rear suspension
as follows:
FRONT AIR SPRING CLEARANCE
1. With the vehicle at normal operating air pres-
sure (95 - 125 psi (655 - 860 kPa)), measure
air spring clearance. This clearance should be
11.7 inches (297.3 mm).
Note:
The measurement should be taken from
underneath the upper air spring support on sub-
frame to top of the lower air spring support on axle
(refer to figure 23 for more details). If adjustment
is required, begin with the drive axle.
2.
Loosen the clamp on the rubber coupling and
bring it up or down (Fig. 24).
Note:
Allow suspension to stabilize before taking
reading.
3.
When the desired height is obtained, tighten
clamp.
REAR AIR SPRINGS CLEARANCE
1.
Refer to XL Maintenance Manual, Section 16,
paragraph "7. SUSPENSION HEIGHT AD-
JUSTMENT".
9. HEIGHT CONTROL VALVE
9.1 Operation
The height control valves automatically add air to,
or release air from air springs to maintain constant
suspension height regardless of load, or load
distribution. Each valve adjusts independently
according to the following conditions:
9.1.1 Loading Position
As the load increases and lowers the vehicle
body, the overtravel lever commands the height
control valve to add air to air springs.
