Chevrolet 30 Series 1967 Service Manual page 127

The frame side rails, cross sills and outriggers are
part of the underbody assembly which is a welded unit
of the body assembly (see Section 1).
Misalignment of the underbody can affect door opening
One method of determining the alignment of the under­
body is with a tram gauge which should be sufficiently
flexible to obtain all necessary measurements up to three
quarters the length of the vehicle. A good tramming tool
is essential for analyzing and determining the extent of
collision misalignment present in underbody construction.
MEASURING (Fig. 8)
To measure the distance accurately between any two
reference points on the underbody, two specifications
are required.
1. The horizontal dimension between the two points
to be trammed.
2. The vertical dimension from the datum line to the
points to be trammed.
The tram bar should be on a parallel to that of the
body plane. The exception to this would be when one
GENERAL DESCRIPTION-CHEVY VAN
UNDERBODY ALIGNMENT
fits and also influence the suspension system, causing
suspension misalignment.
underbody alignment be exact to within ± 1/16" of the
specified dimensions.
of the reference locations is included in the misaligned
area; then the parallel plane between the body and the
tram bar may not prevail.
repairs, the tram gauge should be set at the specified
dimension to check the accuracy of the repair operation.
EXCESSIVE BODY DAMAGE
If damage is so extensive that key locations are not
suitable as reference points, repair operations should
always begin with the underbody area.
ponents should be aligned progressively from this area.
Unlike the conventional type of frame design, the unitized
type of body construction seldom develops the two con­
ditions of " twist" and " diamond" in the underbody area
as a result of front or rear end collisions, therefore,
there usually is an undamaged area suitable as a begin­
ning reference point.
FRAME 2-9
It is essential, therefore, that
After completion of the
All other com­
CHEVROLET TRUCK SERVICE MANUAL