Rear Suspension Repair

On almost any coil rear suspension car and our project ’68 Chevelle, the rear upper and lower control arms locate the rear axle and transmit acceleration, braking, and cornering forces into the frame. The mounting holes in the frame brackets are designed to be perfectly round so the mounting bolts fit tightly and the suspension geometry remains fixed.

If the holes become elongated ("wallowed out"):

- The control arm can shift slightly under load.
- Rear axle alignment can change during acceleration and braking.
- You may hear clunking, popping, or banging noises from the rear suspension.
- Wheel hop can become worse during hard acceleration.
- Handling can feel unstable or unpredictable.
- Additional stress is placed on the control arm bushings, bolts, and frame brackets.
- Cracks can eventually develop around the damaged mounting points.

On a high-torque Chevelle, especially one with a big-block engine, sticky tires, or drag racing use, elongated control arm mounting holes should be considered a structural repair issue rather than simply a nuisance.

Before repairing: Remove the control arm and bolt. Measure the original bolt diameter. Check whether the hole is: Slightly elongated (less than about 1/16 inch oversize) Moderately elongated or Severely damaged or cracked. Also inspect both sides of the bracket, looking for cracks radiating from the hole.

If repairs are needed it is best weld and re-drill the affected area. Gary Simpson demonstrates how to repair elongated suspension holes in both the frame rail and the control arm bracket on our project car.

While we demonstrate the correct way to make the repair avoid making these common mistakes or so-called shortcuts some enthusiasts take:

- Simply tightening the bolt harder.
- Using oversized washers alone.
- Filling the gap with shims.
- Installing a larger bolt without engineering the bracket correctly.
- Ignoring visible cracks.

These approaches usually allow the damage to continue progressing.

After making the repairs needed: install new Grade 8 hardware if the old bolts show wear, inspect the control arm bushings and replace worn bushings, torque all fasteners to factory specifications, verify the rear axle is centered and square in the chassis.

For a 1968 Chevelle that has seen years of use or performance driving, elongated rear control arm mounting holes are common, but a properly welded and re-drilled repair (or welded repair washer repair) can restore full strength and suspension accuracy when done correctly.