Leaf Spring U-Bolt Kit

This procedure replaces the leaf spring U-bolt kit on the rear axle, which secures the axle housing to the leaf springs and includes U-bolts, nuts, and mounting plates.

Warnings

Tools required

Parts

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

Preparation

1. Park vehicle on level, solid ground and engage parking brake
2. Chock the front wheels securely in both directions
3. If U-bolts are rusted, spray with penetrating oil and allow to soak
4. Gather all tools and new U-bolt kit, verifying kit completeness before starting

Procedure

1. 1

   Raise and support vehicle
   Using a floor jack, raise the rear of the vehicle at the frame rails. Place jack stands under the frame rails just forward of the rear axle. Lower the vehicle onto the jack stands, ensuring stable support. The rear axle should hang freely with minimal weight on the suspension.
2. 2

   Position axle support jack
   Place a floor jack under the rear axle differential housing with a block of wood to protect the housing. Raise the jack just enough to contact the axle but not to lift it. This will support the axle when U-bolts are removed and allow for positioning during installation.
3. 3

   Remove U-bolt nuts
   Using a properly-sized socket and ratchet (verify size against the actual U-bolt nuts, commonly 21mm or larger on this heavy-duty application), remove the four nuts from the U-bolts on one side of the axle. The U-bolts pass through the axle mounting plate under the spring and thread into a top plate above the spring. Keep track of any washers. If nuts are seized, use penetrating oil and allow additional soak time.
4. 4

   Remove U-bolts and plates
   Once all four nuts are removed, extract the two U-bolts from the assembly. Remove the top mounting plate. The bottom mounting plate (saddle) may be stuck to the axle housing. Use a pry bar gently if needed to separate it from the axle. Inspect the leaf spring surface where it contacts the axle for damage or debris.
5. 5

   Clean mating surfaces
   Use a wire brush to thoroughly clean the top of the leaf spring pad and the bottom of the axle housing where the mounting plates contact. Remove all rust, dirt, and old paint to ensure proper seating. Clean the U-bolt holes in both mounting plates or use the new plates from the kit.
6. 6

   Position new bottom mounting plate
   Place the new bottom mounting plate (saddle) on top of the leaf spring, centered under the axle housing. The plate should align with the axle housing's centerline. Some plates have locating features or are contoured to fit the axle shape.
7. 7

   Install new U-bolts
   Insert the two new U-bolts down through the holes in the axle mounting plate, around the axle housing, and through the bottom mounting plate and leaf spring. Use the floor jack to adjust axle height if needed to align the U-bolt legs with the holes. The U-bolts should pass through freely without forcing.
8. 8

   Install top plate and nuts
   Place the new top mounting plate over the U-bolt threads. Thread all four nuts onto the U-bolts by hand, ensuring they thread smoothly. Do not tighten yet. Verify that both U-bolts are fully seated and the mounting plates are aligned properly.
9. 9

   Torque U-bolt nuts in sequence
   Tighten the U-bolt nuts in an alternating criss-cross pattern (diagonally opposite nuts) gradually in stages, verifying the sequence per the service manual. Without factory specifications, consult the Mopar service manual for proper torque; the 2007 Ram 3500 rear U-bolt nuts are typically torqued to approximately 150 ft-lbs. Make multiple passes, increasing torque in stages until reaching final torque. This ensures even clamping force.
   ⚠Uneven torque can cause leaf spring damage or U-bolt failure. Use criss-cross pattern and multiple torque passes.
10. 10

    Repeat for opposite side
    If replacing U-bolts on both sides of the axle, repeat steps 3-9 for the opposite side. Maintain axle support with the floor jack throughout the process. Ensure both sides are torqued to the same specification for balanced clamping.
11. 11

    Lower vehicle and settle suspension
    Raise the vehicle slightly with the floor jack, remove the jack stands, and carefully lower the vehicle to the ground. Bounce the rear of the vehicle several times to settle the suspension and allow components to seat properly.
12. 12

    Re-torque U-bolt nuts
    After settling the suspension, re-check and re-torque all U-bolt nuts to specification. It is common for U-bolts to require re-torquing after initial loading. Some manufacturers recommend re-torquing after 50-100 miles of driving.
    ℹ️Schedule a re-torque inspection after 50-100 miles of driving to ensure U-bolts have not loosened during initial break-in.

Reassembly

1. No disassembly beyond U-bolt removal is required for this procedure
2. Ensure all nuts are torqued to proper specification before returning vehicle to service

Verification

• Visually inspect that all U-bolt nuts are properly seated and torqued
• Verify that mounting plates are flush against the leaf spring and axle housing with no gaps
• Check that the axle is centered on the leaf springs with equal spacing on both sides
• Test drive the vehicle and listen for any unusual noises from the rear suspension
• Re-torque U-bolt nuts after 50-100 miles of driving to verify they have not loosened

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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