Rocker panels rot from the inside out, starting at the rear door corner. Replace with Auto Rust Technicians or KEY Parts XJ rockers. Weld in 18-gauge steel patches or full one-piece replacement.
XJ rocker panels rust because dirt and water get trapped between the inner and outer rocker, against the pinch seam. Rust starts behind the rear wheel and works forward.
Replacement panels:
Process (most XJs need full rocker + lower rear quarter + lower front fender bottom):
1) Drill out spot welds along the pinch seam, A/B/C pillar bottoms, and rear wheel opening.
2) Cut out the rotten rocker with a cut-off wheel.
3) Inspect inner rocker structure. Often the inner rocker is also rotted — replace with 18-gauge sheet patches. The unibody structural rail runs inside the rocker — this MUST be repaired or replaced for the vehicle to be safe.
4) Treat all surrounding metal with phosphoric acid (Rust Reformer / Ospho).
5) Tack new rocker in place. Confirm alignment of door gaps.
6) Stitch weld every 1" with MIG (.023 wire, 75/25 gas). Plug-weld through new spot weld holes drilled to match factory pattern.
7) Grind, seam-seal (3M body seam sealer), prime, paint.
This is a 2-3 day job. CRITICAL: do not bondo over rust — the body relies on rocker rigidity. A rotten rocker eats wheel cycling forces and unibody geometry warps. Fix it right or expect bigger problems later.
| Part | Vendor | Est. price |
|---|---|---|
| ART XJ rocker panel pair | Auto Rust Technicians | ~$220 |
| KEY Parts XJ rockers | KEY Parts | ~$200 |
| 3M Body Seam Sealer | 3M | ~$25 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.