GM Service Manual Online
For 1990-2009 cars only

Tram Gauge Method

    • Use a tram gauge as a quick reference in order to determine vehicle damage. Use a tram gauge set with a vertical pointer capable of reaching 914 mm (36 in).
    • Make the engine compartment component measurements from point to point with the vertical pointers equally set.
    • Make the other measurements on the horizontal plane, or the datum line, parallel to the underbody with the vertical pointers set as specified for each point.
    • Measure dimensions that are measured to the gauge holes to the center of the holes and flush to the adjacent surface metal unless otherwise specified. Cross-check the diagonal dimensions in order to verify the dimensional accuracy of the vehicle underbody.

3-Dimensional Method

    • Measure following multiple points when measuring structural repair with repair equipment:
      • The length
      • The height
      • The width
    • Measure 2/3 of the vehicle body in order to obtain accurate comparisons to the vehicle structure.
    • Universal measuring systems combine the equipment and the techniques used to make the underbody 3-dimensional measurements. The universal system provides accurate measurements of the following points:
      • The length
      • The width
      • The height