Chevrolet 1977 light duty truck, Service Manual

Page: 109 / 861

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. FRAME DESIGN
VARIES ACCORDING TO TRUCK MODEL
Fig. 2A-2--C-K-P Series Truck Frame
checking points, with dim ensions for various fram es
shown in figure 2A-3.
Fram e Repair
Welding
Before w elding up a crack in fram e, a hole should
be drilled at the starting point o f the crack to prevent
spreading. W id e n 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 fra m e and encourage new
cracks.
Bolting
W h e re v e r rivets o r failed bolts are replaced, bolt
hole must be as n e a r the O.D. o f the bolt as possible to
p revent bolt from w orking and wearing. Drill out and
line ream hole (or holes) to the bolt O.D.
U N D E R B O D Y A L IG N M E N T
O ne m ethod o f d e te rm in in g the alignm ent o f the
u n d e rb o d y is with a tram gauge which should be
sufficiently felxible to o b ta in all necessary m easurem ents
up to three q uarters the length o f the vehicle. A good
t r a m m in g tool is essential for analyzing and d eterm ining
th e extent o f collision m is a lig n m e n t p re s e n t in
u n d e rb o d y construction.
M E A S U R IN G
To m easure the distance accurately between any two
reference points on the underbody, two specifications are
required.
1. The horizontal dim ension between the two
points to be tram m ed.
2. The vertical dim ension from the d a tu m line to
the points to be tram m ed.
The tram bar should be on a parallel to that o f the
body plane. T he exception to this would be w hen one o f
the reference locations is included in the misaligned
area; then the parallel plane between the body and the
tram b ar m ay not prevail. A fter completion o f the
repairs, the tram gauge should be set at the specified
dim ension to check the accuracy o f the rep air operation.
EXCESSIVE BODY DA M A G E
If d a m a g e is so extensive that key locations are not
suitable as reference points, re p a ir operations should
always begin with the underb o d y area. All other
com ponents should be aligned progressively from this
area. Unlike the conventional type o f fram e design, the
unitized type o f body construction seldom develops the
two conditions o f "tw ist" and " d i a m o n d " in the
underb o d y area as a result o f front or re a r end collisions,
therefore, there usually is an u n d a m a g e d area suitable as
a beginning reference point.