GM Service Manual Online
For 1990-2009 cars only

Condition

Cause

Action

Sag

    • The vehicle is overloaded
    • The load distribution of the vehicle is uneven
    • Abrupt changes in section modulus
    • Improper body or accessory mounting, including the following situations:
       - Holes drilled in the flange of the frame rail
       - Too many holes in the web section of the rail
       - More than four holes in the same vertical line of the rail web
       - Welds on the flange, particularly across the flange or along the edge of the flange
       - Cutting holes in the rail with a torch
       - Cutting notches anywhere on the rails
    • A vehicle fire
    • A vehicle collision
    • The use of improper equipment

Straighten and reinforce the frame. Refer to Frame Repair .

Buckle or Side Sway

    • A vehicle collision
    • A vehicle fire
    • Abrupt changes in section modulus

Straighten and reinforce the frame. Refer to Frame Repair .

Diamond

    • A vehicle collision
    • Towing another vehicle with a chain attached to one corner of the frame

Straighten and reinforce the frame. Refer to Frame Repair .

Twist

    • A vehicle collision
    • Operating the vehicle on very rough terrain

Straighten and reinforce the frame. Refer to Frame Repair .

Improper Tracking

    • The frame is not aligned properly
    • Shifting of the front or rear axle
    • The wheels are out of alignment
    • Straighten and reinforce the frame. Refer to Frame Repair .
    • Realign and secure the axle.
    • Align the wheels. Refer to Wheel Alignment Specifications in Wheel Alignment.

Cracks in the Web of the Rails

    • Loose crossmember attaching bolts
    • Stress concentration. Refer to Minimizing Frame Service Description
    • Replace, or weld and reinforce the rail.
    • Locate the stressed area of the frame:
        1. Ream the bolt holes and install larger bolts if necessary.
        2. Tighten the bolts.