Replace the rear leaf spring U-bolt kit, which secures the rear axle to the leaf springs and includes U-bolts, nuts, and retainer plates.

Warnings

Tools required

Parts

• Leaf spring U-bolt kit (includes 4 U-bolts, 8 nuts, 2 retainer plates per side) × 1 — Use OEM or heavy-duty aftermarket specification

Preparation

1. Park vehicle on level, solid surface and engage parking brake
2. Place wheel chocks in front of both front wheels
3. Loosen rear wheel lug nuts while vehicle is on ground
4. Raise rear of vehicle with floor jack at rear axle differential center
5. Place jack stands under frame rails behind rear axle, then lower vehicle onto stands
6. Remove rear wheels completely
7. Spray penetrating oil on all U-bolt nuts and allow to soak for 10-15 minutes
8. Position floor jack under rear axle differential to support axle weight independently

Procedure

1. 1

   Support the rear axle
   Position the floor jack under the center of the rear differential and raise it just enough to make light contact with the axle housing. The jack stands should still be bearing the vehicle's weight, but the jack prevents the axle from dropping when U-bolts are removed. Verify the axle is stable and level.
2. 2

   Remove driver side U-bolt nuts
   Starting with the driver side, remove all four nuts from the two U-bolts (two nuts per U-bolt). Use a cross-pattern loosening sequence to prevent binding. Remove the nuts completely and keep them separate from new hardware to avoid confusion.
3. 3

   Remove driver side U-bolts and retainer plate
   Pull both U-bolts downward out of the spring pack and axle pad. Remove the lower retainer plate. Inspect the spring pack top surface and axle pad for damage, rust, or irregularities. Wire brush the surfaces clean if needed.
4. 4

   Install new driver side U-bolts and retainer plate
   Position the new lower retainer plate under the spring pack, aligning holes with the spring center bolts. Insert both new U-bolts from the top, through the axle pad, spring pack, and retainer plate. Verify proper seating and alignment before installing nuts.
   ℹ️Ensure the axle is properly centered on the spring pack before installing U-bolts. The centering pin on the spring should engage the hole in the axle pad.
5. 5

   Install and torque driver side U-bolt nuts
   Thread all four new nuts onto the U-bolt threads by hand until finger-tight. Apply anti-seize compound to threads if desired. Using a cross-pattern (front-left, rear-right, front-right, rear-left), torque all nuts to 75 ft-lbs in the first pass, then 90 ft-lbs in the second pass, and finally to manufacturer specification (typically 100-120 ft-lbs for F-150, verify in service manual) in the final pass. Ensure retainer plate draws down evenly.
   ⚠Use a cross-pattern torque sequence to prevent retainer plate distortion. Uneven torque can cause U-bolt failure and axle misalignment.
6. 6

   Remove passenger side U-bolt nuts
   Repeat the removal process for the passenger side. Remove all four nuts from the two U-bolts using a cross-pattern loosening sequence. Verify the floor jack is still supporting the axle before removing nuts completely.
7. 7

   Remove passenger side U-bolts and retainer plate
   Pull both U-bolts downward out of the spring pack and axle pad. Remove the lower retainer plate. Wire brush the spring pack top surface and axle pad clean, removing any rust or debris.
8. 8

   Install new passenger side U-bolts and retainer plate
   Position the new lower retainer plate under the spring pack. Insert both new U-bolts from the top through the axle pad, spring pack, and retainer plate. Verify the axle centering pin is properly engaged and the axle is square to the vehicle before proceeding.
9. 9

   Install and torque passenger side U-bolt nuts
   Thread all four new nuts onto the U-bolt threads by hand. Using the same cross-pattern sequence as the driver side, torque all nuts to 75 ft-lbs, then 90 ft-lbs, then to final manufacturer specification in three progressive passes. Double-check that all nuts on both sides are properly torqued.
10. 10

    Reinstall wheels and lower vehicle
    Reinstall both rear wheels and thread lug nuts by hand. Lower the floor jack supporting the axle. Raise the vehicle slightly off jack stands, remove stands, and lower the vehicle completely to the ground. This loads the suspension with vehicle weight.
11. 11

    Final torque wheel lug nuts
    With the vehicle on the ground, torque all rear wheel lug nuts to specification using a star pattern. Verify all lug nuts are properly seated and torqued.
    Torque spec

    Wheel Lug Nuts169 Nm (125 lb-ft)

Reassembly

1. After 50-100 miles of driving, re-torque all U-bolt nuts to verify proper retention
2. Inspect U-bolt installation for any signs of loosening or retainer plate movement
3. Have a professional alignment check performed if any steering pull or irregular tire wear develops

Verification

• Verify all U-bolt nuts are torqued to specification and seated properly against retainer plates
• Confirm axle is centered on leaf springs with centering pins properly engaged on both sides
• Test drive vehicle at low speed and verify no clunking, shifting, or abnormal handling from rear suspension
• Visually inspect U-bolt installation after 50 miles to confirm no loosening has occurred

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