Curb Height Measurement Air Springs
All pressurized air suspension components contain high pressure air (up to 220 psig). Use extreme caution when inspecting for leaks. Wear safety goggles and adequate protective clothing when inspecting or servicing the air suspension system. A sudden release of air under this amount of pressure can cause possible serious or fatal injury.
Before performing any service on the air suspension system, the system must be disabled to prevent the system from changing ride height. Before any given component is to be serviced it must be deflated. Servicing the air suspension system without the system disabled, or with pressure in any specific component, can cause possible serious or fatal injury.
When removing an air line from a component and the air line is to be reused, do not remove the 90° fitting or the brass fitting from the air line. If either is removed, the air line must be replaced. New components have air line fittings attached; however if the original air line is used the original fitting must also be used. Do not remove protective caps or plugs from air lines or components until ready to install the air line to prevent moisture or dirt intrusion. All air line fittings must be hand started to avoid cross threading.
Carry out an air suspension curb ride height measurement on both sides of the vehicle.
- Level the truck to Normal Ride Height by using the scan tool to perform the "Level to set level" function.
- Measure from the center of the wheel to ground (A).
- Measure from the frame to the ground (B).
- The frame reference point for measurement (B) on vehicles with 140 and 169 inch wheelbase is 127.59 mm (5 in) forward of the frame hole as shown.
- The frame reference point for measurement (B) on vehicles with 149 and 160 inch wheelbase is 76.79 mm (3 in) forward of the frame hole as shown.
- Subtract A from B, for the difference (C). The vehicle range should be:
2500 FRONT 2500 REAR 3500 FRONT 3500 REAR Single Rear Wheel Vehicles (4X2) 88 mm (+/-10 mm) 250.70 mm (+30/-10 mm) 86 mm (+/- 10 mm) 307.19 mm (+30/-10 mm) Single Rear Wheel Vehicles (4X4) 96 mm (+/-10 mm) 296.83 mm (+30/-10 mm) 94 mm (+/- 10 mm) 296.20 mm (+30/-10 mm) Dual Rear Wheel Vehicles (4X2) N/A N/A 86 mm (+/- 10 mm) 307.19 mm (+30/-10 mm) Dual Rear Wheel Vehicles (4X4) N/A N/A 94 mm (+/- 10 mm) 296.20 mm (+30/-10 mm) - Enter the difference C (mm only) into the scan tool.
- With the scan tool, use the air suspension control module (ASCM) routine (Ride Height Calibration), write the following:
- Left Rear Calibrated Height (C1)
- Right Rear Calibrated Height (C2)
- Read Stored Calibration Values Permanent Status "write successful" will appear if the values are within the tolerance range. Otherwise a negative response code will be displayed.