Air Spring/Air Bag

This procedure covers the removal and replacement of rear air spring/air bag assemblies on a 1972 Ford F-100, including disconnection of air lines and mounting hardware.

Warnings

Tools required

Parts

• Air spring/air bag assembly × 1 — Use OEM specification or aftermarket equivalent for rear suspension
• Air line fitting washers/seals × 2 — Use OEM specification
• Upper mounting hardware kit (if corroded) × 1 — Use OEM specification
• Lower mounting hardware kit (if corroded) × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake.
2. Chock the front wheels securely.
3. Locate the air compressor system or air supply valve and shut off air supply to the rear suspension.
4. Depressurize the air spring system by opening the pressure release valve or disconnecting the air supply line at a safe connection point.
5. Raise the rear of the vehicle using a floor jack placed at the rear axle or frame rail.
6. Support the vehicle on jack stands placed under the frame rails behind the cab.
7. Lower the jack slightly so the rear axle is supported but not under full load, allowing the suspension to droop and relieve tension on the air spring.

Procedure

1. 1

   Verify System Depressurization
   Confirm the air spring system is fully depressurized by pressing on the air bag body. It should be completely deflated with no resistance. Listen for any residual air escaping. If pressure remains, locate and open the manual deflate valve or disconnect the air supply line completely.
2. 2

   Disconnect Air Supply Line
   Locate the air supply line connection at the air spring. This is typically a push-to-connect or threaded brass fitting at the top or side of the air bag assembly. For push-to-connect fittings, press the release collar and pull the line free. For threaded fittings, use a 9/16" or 5/8" wrench to disconnect the air line from the air spring body. Cap or plug the air line to prevent contamination.
3. 3

   Remove Upper Mounting Fasteners
   Locate the upper mounting bracket where the air spring attaches to the frame rail or bed mounting point. Remove the 2 upper mounting bolts using a 5/8" or 3/4" socket and ratchet. These bolts typically pass through the air spring mounting plate and thread into captive nuts or frame bracket. If fasteners are corroded, apply penetrating oil and allow to soak before attempting removal.
4. 4

   Support the Air Spring
   With the upper fasteners removed, support the air spring assembly by hand or with a bungee cord to prevent it from falling when the lower mount is disconnected. The air spring will still be attached at the lower mount point.
5. 5

   Remove Lower Mounting Fasteners
   Locate the lower mounting bracket where the air spring attaches to the rear axle housing or axle mounting plate. Remove the 2 lower mounting bolts using a 5/8" or 3/4" socket and ratchet. These bolts typically secure the air spring base to a bracket welded or bolted to the axle. Support the air spring as you remove the final fastener.
6. 6

   Remove Air Spring Assembly
   Carefully maneuver the air spring assembly out from between the frame and axle. Depending on installation configuration, you may need to rotate or angle the assembly to clear surrounding components such as the rear shock absorber, brake lines, or frame cross members. Inspect the removed air spring for damage, leaks, or excessive wear.
7. 7

   Inspect Mounting Surfaces and Hardware
   Clean both upper and lower mounting surfaces with a wire brush, removing rust, dirt, and old thread locker. Inspect mounting brackets for cracks, excessive rust, or distortion. Check all fastener threads for damage. Replace any compromised hardware before installing the new air spring.
8. 8

   Position New Air Spring
   Position the new air spring assembly between the frame rail and rear axle, aligning the upper mounting plate with the frame bracket. Ensure the air fitting port is oriented for easy air line connection and that the air spring bellows will not contact any sharp edges or moving components during suspension travel.
9. 9

   Install Lower Mounting Fasteners
   Align the lower air spring bracket with the axle mounting bracket. Install the 2 lower mounting bolts finger-tight. Ensure the air spring base is properly seated and centered on the mounting bracket before tightening. Tighten the lower mounting bolts securely using a 5/8" or 3/4" socket, alternating between bolts to ensure even seating.
10. 10

    Install Upper Mounting Fasteners
    Align the upper air spring bracket with the frame rail mounting bracket. Install the 2 upper mounting bolts finger-tight. Verify proper alignment and that the air spring is not twisted or misaligned. Tighten the upper mounting bolts securely using a 5/8" or 3/4" socket, alternating between bolts.
11. 11

    Connect Air Supply Line
    Connect the air supply line to the air spring fitting. For push-to-connect fittings, insert the air line fully into the fitting until you hear or feel a click. Tug gently to verify it is locked. For threaded fittings, install new sealing washers if provided, then thread the fitting hand-tight and finish with a 9/16" or 5/8" wrench, tightening an additional 1/4 to 1/2 turn past hand-tight.
12. 12

    Pressurize and Leak Test
    Remove jack stands and lower the vehicle to the ground. Restore air supply to the system and pressurize the air spring to normal operating pressure. Apply soapy water solution to all air line connections and fittings, watching for bubbles that indicate air leaks. If leaks are detected, depressurize the system and retighten or reseal the affected connection.

Reassembly

1. If replacing both rear air springs, repeat the procedure for the opposite side.
2. Verify all mounting fasteners are tight and all air line connections are secure.
3. Check that the air spring bellows has proper clearance from the frame, axle, shock absorbers, and brake components through full suspension travel.

Verification

• With the vehicle on level ground and the air system pressurized to normal operating pressure, verify both air springs are inflated evenly.
• Bounce the rear of the vehicle to cycle the suspension and verify the air springs compress and extend smoothly without binding or contact.
• Re-check all air line connections for leaks using soapy water solution.
• Test drive the vehicle and verify normal ride height, proper suspension function, and no air leaks or unusual noises from the rear suspension.

More procedures for this vehicle