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 measuring checks must include a vertical pointer capable of reaching 457 mm (18 in).

The following two 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

Equally set the vertical pointers. 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 metal unless otherwise specified. It is recommended that the diagonal dimensions be cross body checked on both sides in order to verify the dimensional accuracy of the vehicle underbody.