Chevrolet 1977 light duty truck Service Manual page 109

checking points, with dimensions for various frames
shown in figure 2A-3.
Fram e Repair
Welding
Before welding up a crack in frame, a hole should
be drilled at the starting point o f the crack to prevent
spreading. W id en V groove crack to allow complete weld
penetration.
N O T E: Do not weld into corners o f fram e or along
edges o f side rail flanges. W elding at these points
will tend to weaken the fram e and encourage new
cracks.
Bolting
W herever rivets or failed bolts are replaced, bolt
hole must be as n e ar the O.D. o f the bolt as possible to
prevent bolt from w orking and wearing. Drill out and
line ream hole (or holes) to the bolt O.D.
U N D ER B O D Y A L IG N M E N T
O ne m ethod o f d eterm ining the alignm ent of the
u n derbo dy is with a tram
sufficiently felxible to o btain all necessary measurements
up to three quarters the length o f the vehicle. A good
tra m m in g tool is essential for analyzing and determ ining
the extent o f collision
underbo dy construction.
DIMENSIONS TO HOLES OR SLOTS ARE MEASURED TO THE CENTER OF HOLE OR SLOT
GAUGE HOLES ARE 5/8" DIAMETER
© INDICATES THAT THE DIMENSION IS TO THE UNDERSIDE OF THE FRAME TOP
SURFACE OR INSIDE OF THE FRAME OUTER SURFACE
NOTE: FRAME ILLUSTRATED IS TYPICAL.
VARIES ACCORDING TO TRUCK MODEL
Fig. 2A-2--C-K-P Series Truck Frame
gauge which should be
m isa lig n m e n t p resent in
FRAME DESIGN
M E A S U R IN G
To measure the distance accurately between any two
reference points on the underbody, two specifications are
required.
1. The horizontal dimension
points to be trammed.
2. The vertical dim ension from the datu m line to
the points to be trammed.
The tram bar should be on a parallel to that o f the
body plane. The exception to this would be when one o f
the reference locations is included in the misaligned
area; then the parallel plane between the body and the
tram bar may not prevail. A fter completion of the
repairs, the tram gauge should be set at the specified
dimension to check the accuracy o f the repair operation.
EXCESSIVE BODY DAM AG E
If dam age is so extensive that key locations are not
suitable as reference points, rep air operations should
always begin with the
components should be aligned progressively from this
area. Unlike the conventional type of fram e design, the
unitized type o f body construction seldom develops the
two conditions o f "twist"
underbody area as a result o f front or rear end collisions,
therefore, there usually is an u n dam ag ed area suitable as
a beginning reference point.
between the two
underbody area. All other
and " d ia m o n d " in the