GM Service Manual Online
For 1990-2009 cars only

Using improper techniques causes many weld and/or frame failures. The following information points out the potential areas of difficulty and provides some general guidelines for successful frame welding.

Most weld failures occur at the end of the weld in the areas of the frame that are under high stress. By eliminating the ends of a weld, you may reduce failures.

  1. Make a hole or a slot in the part to be attached.
  2. Use a fillet weld around a slot or a plug weld.
  3. Do not leave a notch at the end of a weld.

Over-welding may be harmful, especially if the overwelding occurs in an area of the frame that receives high concentrations of stress.

Small cracks in a crossmember may be welded. Refer to Frame Repair . While welding, follow these rules:

  1. The frame is covered with a protective wax coating. Use a wire brush in order to remove any concentration of wax before welding. After welding, recoat the area with new wax.
  2. Do not use oxyacetylene welding equipment.
  3. Whenever possible, use smaller diameter electrodes and make several passes. This is preferred to using a large diameter electrode and making fewer passes.
  4. Do not use more heat than necessary in order to give good penetration.
  5. Ensure that the weld is free from craters and undercuts.
  6. Ensure that the scale is removed from each successive pass.
  7. If you are repairing a crack, grind the surface of the weld so that the surface is flush with the parent material.
  8. When mounting accessories, do not weld across the flanges.
  9. When mounting accessories, do not weld within 19 mm (3/4 in) of a flange.
  10. Do not weld up to the edge of the part that is being welded to a frame. Leave approximately 6 mm (1/4 in) between the end of the weld and the edge of the part.
  11. Do not weld cast brackets to the frame.
  12. Do not weld the flanges of cracked reinforcements and base rails together.
  13. Do not attach the ground cable to the engine. Connect the welding machine ground cables as close to the working area as possible.
  14. Disconnect the vehicle batteries.
  15. Do not get the welding cables near the vehicle wiring. Avoid contact between the welding cables and any part of the vehicle.