GM Service Manual Online
For 1990-2009 cars only

Use a measuring tram gauge as an accurate method of determining the alignment of the underbody. The tram gauge set required to perform the recommended measurements must include a vertical pointer capable of reaching 457 mm (18 in).

The following 2 types of measurement may be made using a tram gauge:

    • Direct point to point measurements
    • Measurements calculated on a horizontal plane (datum line), parallel to the underbody

Set the vertical pointers equally. Take the point to point measurements on the following components:

    • The steering components
    • The suspension components
    • The engine compartment components

Dimensions that are measured to gauge holes are measured to the center of the holes and flush to the adjacent surface meta, unless otherwise specified. Cross-body measure the diagonal dimensions on both sides of the vehicle in order to verify the dimensional accuracy of the underbody.