Chevrolet 1980 Light Duty Truck Service Manual page 108

2A -4 FRAME
Frame Repair
Welding
Before welding up a crack in frame, a hole should be
drilled at the starting point of the crack to prevent
spreading. Widen V groove crack to allow complete weld
penetration.
Do not weld into corners of frame or along
NOTICE:
edges of side rail flanges. Welding at these points will
tend to weaken the frame and encourage new cracks.
Bolting
Wherever rivets or failed bolts are replaced, bolt hole
must be as near the O.D. of the bolt as possible to prevent
bolt from working and wearing. Drill out and line ream hole
(or holes) to the bolt O.D.
UNDERBODY A LIG N M E N T
One method of determining the alignment of the
underbody is with a tram gage which should be sufficiently
felxible 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
To measure the distance accurately between any two
reference points on the underbody, two specifications are
Fig. 2A-4-G Van Truck Reference Dimensions
required.
to be trammed.
points to be trammed.
plane. The exception to this would be when one of the
reference locations is included in the misaligned area; then
the parallel plane between the body and the tram bar may
not prevail. After completion of the repairs, the tram gage
should be set at the specified dimension to check the
accuracy of the repair operation.
EXCESSIVE BODY D AM AG E
suitable as reference points, repair operations should always
begin with the underbody area. All other components
should be aligned progressively from this area. Unlike the
conventional type of frame design, the unitized type of body
construction seldom develops the two conditions 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 beginning reference point.
1. The horizontal dimension between the two points
2. The vertical dimension from the datum line to the
The tram bar should be on a parallel to that of the body
If damage is so extensive that key locations are not
LIG H T T R U C K S ER V IC E M AN U A L