GM Service Manual Online
For 1990-2009 cars only

The frame consists of the following components:

    • The side rails carry the load.
    • The crossmembers stabilize the rails.

Body misalignment is divided into the following types:

    • Sag
    • Collapse
    • Diamond
    • Sidesway
    • Twist

A misaligned frame may move from its proper position in the following ways:

    • Forward
    • Up or down
    • To the side

Check all possibilities. The easiest way to check body alignment is with tramming gauges and universal measuring systems made for this purpose. Detailed instructions normally come with the equipment at the time of purchase. Refer to those instructions.

Always park the vehicle on a level surface. Certain conditions call for preliminary checks before you actually check the frame. The vehicle may mistakenly appear misaligned under the following conditions:

    • When suspension or axle problems are present
    • When an axle shifts, causing a diamond or sidesway incorrectly to appear
    • When the springs are weak

Visually inspect the top and bottom flanges of each rail. This step may reveal the specific area where sag or a buckle exists. In case of a sag, wrinkles may appear on the top of the upper flange. Wrinkles on the bottom flange indicate a buckle.