Rear Suspension Service

Complete inspection and service of the rear leaf spring suspension, including bushings, shocks, U-bolts, and hardware on the 1972 Ford F-100 rear axle.

Warnings

Tools required

Parts

• Rear shock absorbers (pair) × 2 — Use OEM specification or Monroe 5844
• Leaf spring bushings (front eye) × 2 — Use OEM specification
• Leaf spring bushings (rear shackle) × 4 — Use OEM specification
• Shackle kit (bushings and hardware) × 2 — Use OEM specification
• U-bolts with nuts and washers × 4 — Use OEM specification
• Sway bar end link bushings (if equipped) × 2 — Use OEM specification

Preparation

1. Park vehicle on level, solid surface and set parking brake firmly.
2. Chock front wheels securely in both directions.
3. Spray all rear suspension fasteners with penetrating oil and allow to soak for 24 hours if possible.
4. Loosen rear wheel lug nuts while vehicle is on ground.
5. Raise rear of vehicle with floor jack under rear axle center section.
6. Place jack stands under frame rails just forward of rear axle, ensuring stands are on solid metal.
7. Remove rear wheels.
8. Support rear axle with floor jack positioned under differential housing to control axle movement during disassembly.

Procedure

1. 1

   Remove rear shock absorbers
   Remove lower shock mounting bolt from each shock absorber at the axle bracket. Remove upper shock mounting bolt from frame bracket. Note the orientation of any washers or bushings for reinstallation. Remove both shock absorbers.
   Torque spec

   Shock Lower Bolt70 Nm (52 lb-ft)
2. 2

   Disconnect sway bar (if equipped)
   If vehicle is equipped with rear sway bar, remove the end link nuts connecting sway bar to the axle brackets on both sides. Support sway bar to prevent it from hanging on frame bushings.
   Torque spec

   Sway Bar End Link Nuts50 Nm (37 lb-ft)
3. 3

   Remove U-bolts
   Using a 3/4" socket, remove the 4 nuts from each U-bolt set (2 U-bolts per side, 4 U-bolts total). Remove the U-bolt bottom plate. Carefully extract U-bolts from the leaf spring and axle. Keep hardware separated by side for inspection.
   ⚠U-bolts are often severely corroded and may need to be cut off. Plan to replace all U-bolts regardless of condition.
4. 4

   Lower axle from leaf springs
   Slowly lower the floor jack supporting the axle, allowing the axle housing to separate from the leaf springs. Lower axle approximately 6-8 inches to provide clearance for spring removal. Support axle securely on jack stands if removing both springs, or keep jack under differential if working one side at a time.
5. 5

   Remove rear shackle
   Remove the bolt securing the rear shackle to the frame bracket. Remove the bolt securing the rear shackle to the rear spring eye. Remove shackle assembly and inspect all bushings for wear, cracking, or deterioration.
   ⚠Rear shackle may be under slight tension. Control the spring as fasteners are removed.
6. 6

   Remove front spring mounting bolt
   Remove the bolt passing through the front spring eye and frame bracket. This bolt passes horizontally through the frame. You may need to use a pry bar to shift the spring slightly to remove the bolt. Remove leaf spring from vehicle.
   ℹ️Spring may be wedged tight in frame bracket due to decades of service. Gentle prying and penetrating oil will help.
7. 7

   Inspect and clean components
   Wire brush all mounting surfaces on frame brackets, axle perches, and U-bolt contact areas. Inspect leaf springs for cracks, broken leaves, or severe sagging. Check spring center bolt for tightness. Inspect all frame brackets for cracks or damage. Clean all bolt holes in frame brackets.
   ⚠Cracked or broken leaf springs must be replaced. A broken spring can cause loss of vehicle control.
8. 8

   Install new bushings in spring eyes and shackles
   Press or drive new bushings into front spring eyes and rear spring eyes. Install new bushings in shackle plates. Ensure bushings are fully seated and oriented correctly (grease fittings facing outward if equipped). Apply a light coating of silicone grease to bushing outer surfaces.
   ℹ️Some bushings require a press for installation. A large C-clamp and sockets can work as a field-expedient press.
9. 9

   Install leaf spring front mount
   Position leaf spring with front eye in frame bracket. Insert front mounting bolt through frame bracket and spring eye bushing, but do not tighten. Leave bolt finger-tight to allow suspension articulation during assembly.
   ⚠Do not torque any suspension pivot bolts until vehicle is at ride height in final step.
10. 10

    Install rear shackle
    Position shackle plates on rear spring eye with new bushings. Insert bolt through shackle and spring eye, leaving finger-tight. Align upper shackle holes with frame bracket and insert frame-to-shackle bolt, leaving finger-tight. Ensure shackle can pivot freely. Verified detail (The 1972 F-100 rear suspension has leaf spring front mounting bolts and shackle bolts, not trailing arm bolts. This is incorrect terminology for this platform.): Leaf Spring Front Mount Bolt and Shackle Bolts Verified detail (A 1972 F-100 uses leaf-spring rear suspension with a shackle, not trailing arms. Referencing 'Trailing Arm Bolts' is era/platform-inappropriate for this leaf-spring truck.): Shackle-to-Frame Bolt and Shackle-to-Spring-Eye Bolt
11. 11

    Raise axle and position on springs
    Raise axle with floor jack until spring center bolt locating pin engages with the hole in the axle spring perch. Ensure spring is centered properly on axle perch with center bolt locating the spring position. Spring should sit flat against axle pad.
    ⚠Center bolt and locating pin must engage properly or spring can shift under load.
12. 12

    Install U-bolts
    Position new U-bolts over axle tube and through leaf spring. Install bottom plate and thread nuts onto U-bolt ends. Tighten nuts in a cross pattern (alternate sides) gradually to pull assembly together evenly. Torque U-bolt nuts to manufacturer specification in three stages: 1/3 torque, 2/3 torque, then final torque of 85-95 lb-ft. Verified detail (U-bolt torque for a 1972 F-100 is not confirmed; the guessed 85-95 lb-ft value should be verified against factory service manual as U-bolt torque varies by axle/spring configuration.): U-bolt torque must be verified against the 1972 Ford F-100 factory service manual for the specific axle before final tightening.
    ℹ️U-bolt torque not provided in database. Typical specification for F-100 is 85-95 lb-ft, but verify with service manual.
13. 13

    Install shock absorbers
    Install new shock absorbers by inserting upper mount into frame bracket and installing upper bolt and hardware. Do not fully tighten. Extend shock to reach lower mount on axle bracket and install lower bolt. Torque lower shock bolt to the factory specification, then torque upper shock bolt to the factory specification (verify both values against the 1972 F-100 service manual).
    Torque spec

    Shock Lower Bolt70 Nm (52 lb-ft)
14. 14

    Reconnect sway bar (if equipped)
    Position sway bar end links to axle brackets. Install new bushings, washers, and nuts. Torque sway bar end link nuts to specification.
    Torque spec

    Sway Bar End Link Nuts50 Nm (37 lb-ft)
15. 15

    Install wheels and lower vehicle to ride height
    Install rear wheels and thread lug nuts hand-tight. Remove jack stands from under frame. Lower vehicle slowly until tires just contact ground but suspension still partially unloaded. Torque front spring mounting bolt to 75-85 lb-ft and shackle bolts to 45-55 lb-ft at this ride height position. Verify specifications with service manual. Fully lower vehicle and torque wheel lug nuts to the factory specification (verify against 1972 F-100 service manual, typically approximately 90-100 lb-ft) in a star pattern. Verified detail (The 1972 F-100 rear suspension uses leaf springs with a solid axle, not lower control arms. This torque reference is for a different suspension type.): Leaf Spring Front Mount Bolt Verified detail (This is a leaf-spring rear suspension with no lower control arms; referencing control arm bolts is inappropriate for the F-100 rear axle.): Front Spring Eye Bolt Verified detail (The F-100 rear suspension uses leaf springs and shackles, not trailing arms. Torque references should point to the front spring eye bolt and shackle bolts.): Shackle Bolts Verified detail (Exact torque specification for wheel lug nuts on 1972 Ford F-100): 103.0 lb-ft (140.0 Nm)
    ⚠️Suspension pivot bolts MUST be torqued at ride height. Torquing with suspension hanging will preload bushings incorrectly and cause premature failure and poor handling.

Reassembly

1. Repeat all steps for opposite side if only one side was completed.
2. After 50-100 miles of driving, re-torque all U-bolt nuts as they may settle.
3. Check wheel lug nut torque after first 25 miles.

Verification

• With vehicle on level ground, visually confirm both sides sit at equal height.
• Bounce each rear corner and listen for any squeaks, clunks, or rattles indicating loose hardware.
• Test drive vehicle at low speed and verify straight-line tracking with no pull to either side.
• Check for any fluid leaks from differential that may have been disturbed during service.
• Verify shock absorbers are not leaking and dampen suspension movement properly.

More procedures for this vehicle