Important: Sectioning procedures have been developed to simplify repair to the lower rails, providing the majority of the damage can be returned to factory specifications. This allows the damaged front section to be replaced without performing full rail replacement. Bumper mounting brackets can be serviced separately.

1. Visually inspect and restore as much of the damage as possible to factory specifications.
2. Remove lower tie bar support brace (1)
3. Remove damaged portion of original rail.



4. Remove all related panels and components as necessary.

Important: Removal of the cradle and powertrain is not necessary when performing this procedure.

5. Locate the cut location on the left front rail. Use the left front cross-member cagenut slot for reference.
6. At the front edge of the slot, measure 335 mm (approximately 13-3/8  in) forward. This is the cut location on damaged part.
7. Use a straight edge to scribe a line around the rail.
8. Cut and discard the damaged portion of rail.



9. Cut and remove approximately 5 mm (1/4 in) of the outboard and downward turned flanges from the end of the original rail (1).
10. Cut a 5 mm (1/4 in) gap approximately 5 mm (1/4 in) along the corners of the orginal rail to create a 5 mm (1/4 in) tab for the service part to slide over.



11. Slightly bend the tabs inward to allow the replacement lower rail section to fit over the original rail (1).
12. Apply weld-through coating to all bare metal areas as necessary before fitting service part.

1. Locate the cut location on the service part. Use the front crossmember cagenut slot for reference.
2. Measure 330 mm (13-1/8 in) forward from front edge of slot. This will be the cut location for the service part.
3. Use a straight edge to scribe a line around the rail.
4. Cut and remove front portion of the rail.
5. Discard unused rear portion of the service part.
6. Clean burrs on inside of the rail.
7. Apply weld-thru primer to bare metal surfaces as necessary.

1. Position the modified service part over the tabs of the original rail and allow 5 mm (1/4 in) of overlap.
2. Clamp in place.
3. Check fit using 3-dimensional measuring equipment.
4. Stitch weld along the entire sectioning joint. Make 25 mm (1 in) welds along the seam with 25 mm (1 in) gaps between them.
5. Go back and complete the stitch weld. This will create a solid joint with minimal heat distortion.
6. Clean and prepare welded surfaces.

Important: Prior to refinishing, refer to GM 4901MD-99 Refinish Manual for recommended products. Do not combine paint systems. Refer to paint manufacturer's recommendations.

7. Apply the following:

•	2-part catalyzed primer

•	anti-corrosion protection materials

•

sealers

8. Install all related panels and components.