Suspension Height Control Valve Check
Warning: Inspect the height control components and check their operation. Failure to perform these inspections and checks could result in separation of worn suspension components and loss of vehicle control, possibly causing personal injury or death, or property damage.
- Park the vehicle on a level surface. Apply the parking brake and chock the tires to prevent the vehicle from moving.
- Inspect the front and rear suspensions for any signs of damage, loose components, wear, or cracks. Replace any damaged components to prevent failure or equipment breakdown.
- Inspect all bolts and nuts at the pivot axle connections to assure that they are properly torqued. Check all other nuts and bolts for proper torque. See General Maintenance Schedule Information of this manual for proper torque specifications.
- Check the air pressure gauge to confirm that there is in
excess of 65 psi (448 kPa) in the air system, and inspect the air
springs for sufficient and equal firmness.
Table 1, Suspension Torque Specifications (lubricated threads)
Description
Size
Torque: lbf·ft (N·m)
Shock Absorber Mount Locknut
3/4–16
110 to 150 (149 to 203)
Air Spring Upper Mounting Plate Locknut
3/4–16
31 to 42 (42 to 57)
Air Spring Upper Mounting Plate Capscrew
1/2–13
31 to 42 (42 to 57)
Air Spring Lower Mounting Plate Capscrew
1/2–13
31 to 42 (42 to 57)
Transverse Beam Bushing Locknuts
1-1/4–12
600 to 700 (814 to 949)
Equalizing Beam Center Bushing Locknut
3/4–16
150 to 200 (203 to 271)
Equalizing Beam Front Bushing Locknut
1-1/8–12
600 to 700 (814 to 949)
1-1/4–12
Control Rod Ball Stud Locknut
1-1/8–12
550 to 650 (746 to 881)
Control and Torque Rod Mounting Locknuts
5/8–18
110 to 150 (149 to 203)
Table 1, Suspension Torque Specifications (lubricated threads)
- Check the ride height of the air suspension by measuring
the distance from the center of the lower shock bolt to the bottom
of the frame rail. See Fig.. See Table. for height
control valve adjustment measurements. If ride height is incorrect,
adjust the air suspension.
Table 2, Height Control Valve Adjustment Measurements
Suspension
Measurement
Inches ±1/4 (mm ±6)
AS120 (front)
10 (254) or
10-1/2 (267) 1
AS140 (front)
11 (279)
IFS114 (front)
17-1/2 (445)
IFS ZF (front)
15-3/4 (400)
ADL-RS17/19/21
10-1/4 (260)
AD200-RS17/19
9-3/4 (248)
AD200-RS15
9-3/8 (238)
ADTB280 (rear)
17-1/4 (438)
Airliner 15k (rear)
8-3/4 (222)
AD123 (rear)
18 (457)
ADL123 (rear)
11 (279)
- Some vehicles have a different shock location. When this is the case, the vehicle will have a 55 degree wheel cut. Ride height for these vehicles should be set at 10-1/2 inches (267 mm).
Table 2, Height Control Valve Adjustment Measurements
-
Measure here for suspension ride height.
-
Frame Rail
-
Axle Housing
-
Axle Centerline
Fig. 1, Ride Height Inspection (typical Neway suspension shown)
Note: Height control valves control all front and rear suspension air springs. Check for air leaks by applying a soapy solution. Then, check for bubbles at all air connections and fittings.