Overlap/Backing Plate Sectioning Welding

Caution: Refer to Approved Equipment for Collision Repair Caution in the Preface section.

1. Fit the service panel to the vehicle to ensure a proper fit.
2. Measure and mark a line at the sail panel 120 mm (4 3/4 in) from the back glass opening and 70 mm (2 3/4 in) rearward from the rocker panel locating hole edge of the service panel.
3. Cut along the line to trim the service panel.
4. Fabricate a 50 mm (2 in) backer plate so that the panel will fit behind the sectioning joint at the sail panel.
5. Fabricate a 100 mm (4 in) backer plate for the rocker panel.
6. Drill 8 mm (5/16 in) plug weld holes as necessary in the locations noted from the original panel.
7. Bevel the sail panel and service panel edges at the sectioned area to approximately 10 degrees.
8. Grind a 50 mm (2 in) area of the outer surface on the vehicle to remove any corrosion, E-coat, primers, coatings and galvanizing that may be present.
9. At the section area on the service panel, grind a 50 mm (2 in) area of the back side to remove any corrosion, E-coat, primers, coatings and galvanizing that may be present.
10. Drill plug weld holes approximately 13 mm (1/2 in) from the edge of the cuts the sectioning areas of the service panel and the original panel.
11. Prepare all mating surfaces as necessary.
12. Apply GM-approved weld-thru coating or equivalent to all mating surfaces. Refer to Anti-Corrosion Treatment and Repair .
13. Position and clamp or screw the backer plate with half of the backer plate exposed at the sectioning joint.

Important: Leave a gap of 1 1/2 times the thickness of the metal at the sectioning joint to the original panel.

14. Position the service panel to overlap the backer plate and 1 1/2 times the thickness up to the original panel.
15. Check for proper fit and alignment to the vehicle. Clamp the panels together.
16. Plug weld the backer plate accordingly.
17. Stitch weld along the entire sectioning joint, make 25 mm (1 in) welds along the seam with 25 mm (1 in) gaps between them.
18. Complete the stitch weld.
19. Clean and prepare all welded surfaces of the entire sectioning joint.

Important: Always follow the system manufacturer's instructions for application, handling, and curing.

20. Apply a lightweight body filler to the backer plate area.

Overlap/Backing Plate Sectioning Bonding/Overlap

Important: Before starting the repair, refer to Metal Panel Bonding for proper adhesive applicator preparations and general information.

1. Fit the service panel to the vehicle to ensure a proper fit of a maximum 25 mm (1 in) overlap.
2. Grind a 25 mm (1 in) area of the outer surface on the vehicle panel to remove any corrosion, E-coat, primers, coatings and galvanizing that may be present  (1).
3. At the section joint on the service panel, grind a 25 mm (1 in) area of the back side to remove any corrosion, E-coat, primers, coatings and galvanizing that may be present (2).
4. Bevel the service panel at the section edge to approximately 10 degrees (3).
5. Clean the mating surfaces.

Important: The adhesive has a 40-50 minute working time.

6. Apply a 3-6 mm (1/8-1/4 in) bead of metal panel bonding adhesive to both of the mating surfaces.
7. Using small acid brush, spread a coat of adhesive to cover all the bare metal surfaces to ensure corrosion protection.

Important: DO NOT pull the service panels apart after the panels have been joined together. Slide the panels against each other to realign the panels.

8. Apply a 9-13 mm (3/8-1/2 in) bead of metal panel bonding adhesive to the sectioning part mating surfaces.
9. Position the service panel to the body. Clamp the service panel into position.
10. Install the screws or clamp the overlap sectioning location.
11. Using lacquer thinner, remove the excess adhesive from the overlap section.
12. Allow the adhesive to cure. Remove the screws or clamps from the overlap section.
13. Remove any remaining adhesive where body filler will be applied.
14. Recess the screw holes with a punch and hammer as necessary.

Important: Always follow the system manufacturer's instructions for application, handling, and curing.

15. Apply a fiberglass-filled body filler for the overlap section and screw holes for the first coat.
16. Apply a lightweight body filler to the overlap section for the second coat.