Frame; Underbody Alignment; Measuring; Excessive Body Damage - Chevrolet CHEVY VAN G10 SERIES Service Manual

The fram e side rails, cross sills and outriggers are part o f the
u n d erbody assembly w hich is a w elded u n it o f the body
assem bly (see Section 1).
Misalignment o f th e underb o dy can affect door opening fits
UNDERBODY A LIG N M E N T
One m etho d o f determ ining the alignm ent o f the u n d er­
b o d y is w ith a tram gauge w hich should be sufficiently flexible
to o btain all necessary m easurem ents up to three quarters the
length o f the vehicle. A good tram m ing to o l is essential for
analyzing and determ ining the ex ten t o f collision m isalignment
present in underbody construction.
MEASURING (Fig. 1)
To measure the distance accurately betw een any tw o
reference points on the un d erbo d y, tw o specifications are
required.
1. The horizontal dim ension betw een the tw o points to be
tram m ed.
2. The vertical dim ension from the datum line to the points
to be tram m ed.
The tram bar should be on a parallel to th a t o f the body
SECTION 2

FRAME

GENERAL DESCRIPTION
and also influence th e suspension system , causing suspension
misalignment. It is essential, therefore, th a t underbody align­
m ent be exact to w ithin — 1 /16" o f the specified dimensions.
plane. The exception to this w ould be w hen one o f the
reference locations is included in th e misaligned area; th en the
parallel plane betw een the body and the tram bar may n o t
prevail. A fter com pletion o f th e repairs, th e tram gauge should
be set at the specified dim ension to check th e accuracy o f the
repair operation.

EXCESSIVE BODY DAMAGE

as reference p oints, repair operations should always begin w ith
the underb o d y area. All o th er com ponents should be aligned
progressively from th is area. Unlike th e conventional ty p e of
frame design, th e u n itized ty p e o f body co n stru ctio n seldom
develops the tw o conditions o f " tw ist" and " diam ond" in the
underbody area as a result o f fro n t or rear end collisions,
th e re fo u , th ere usually is an undam aged area suitable as a
beginning reference point.
If damage is so extensive th a t key locations are n o t suitable
C H E V Y V A N S H O P M A N U A L