GM Service Manual Online
For 1990-2009 cars only

Condition

Action

Loads greater than the frame is designed to carry causes sag.

Straighten and reinforce the frame. Refer to Frame Straightening Description .

Uneven load distribution causes sag.

Abrupt changes in the section modulus.

Improper body, or accessory mounting, which may include the following:

    • Holes drilled in the flange of the frame rail.
    • Too many holes in the web section of the rail.
    • Holes in the web section which are too close to each other.
    • Four or more holes in the same vertical line of the rail web.
    • Welds on the flange, particularly across the flange or along its edge.
    • Cutting holes in the rail with a torch.
    • Cutting notches anywhere on the rails.

A collision involving the vehicle causes the following conditions:

    • Sag
    • Buckle
    • Sidesway
    • Diamond

The use of equipment for which the frame has not been designed or reinforced causes the following conditions:

    • Sag
    • Buckle
    • Sidesway