Cab corner rust is nearly universal on 73–87 Square Body trucks from rust-prone areas. If you don’t have welding equipment, there are still solid options for fixing cab corners. Here’s how.
Why Cab Corners Rust:
The cab corner where the lower door jamb meets the rocker panel traps moisture and debris. Combined with poor factory drainage, rust starts from the inside out and eventually eats through the outer skin.
No-Weld Repair Options:
Option 1: Panel Adhesive (Best No-Weld Option)
Panel bonding adhesive (3M 08115 or Lord Fusor) allows you to glue a new cab corner patch panel onto the cleaned surface. This is a legitimate body repair used in professional shops.
Steps:
- Cut out the rusted section cleanly
- Fabricate or purchase a patch panel
- Clean both mating surfaces to bare metal
- Apply panel adhesive
- Press patch into place and clamp
- Allow to cure (24 hours)
- Body filler as needed, prime, and paint
Option 2: Fiberglass Repair (Surface Only)
For small pin holes or thin areas, a fiberglass repair kit can work as a stopgap. NOT suitable for structural areas.
Option 3: Professional Body Shop
If the rust is extensive, a professional shop can TIG/MIG weld in new cab corner sections for $500–$1,500 per corner.
Proper Preparation (The Most Important Step):
Regardless of repair method:
- Rust-Oleum 2-in-1 Rust Converter Spray – Apply to any remaining rust inside the cavity before closing it up
- Seam seal all repaired edges inside and out
- Apply internal cavity wax inside the repaired area
Long-Term Preservation After Repair:
Any cab corner repair is only as good as the moisture barrier you create. Seal every edge, drain any trapped areas, and inspect annually.
The Best Long-Term Fix:
While no-weld repairs work, welded patch panels are the most durable. If you’re keeping the truck long-term, consider paying a shop for proper weld-in repairs.
Has anyone done no-weld cab corner repairs on their Square Body? How did it hold up?