Chevrolet LIGHT DUTY TRUCK (SERIES 10-35) Service Manual page 109

2A-2 FRAME
Tram m ing Sequence (Fig. 2A -1)
1 . Dimensions to bolts and/or holes in frame extend
to dead center of the hole or bolt.
2. Dimensions must be within 3/16".
3. If a tram bar is used, for horizontal alignment "X"
- check from opposite and alternate reference points AA,
BB and CC, as illustrated by the lines in Figure 2A-1. Error
will result if a tram bar is not level and centered at the
reference points.
4. Obtain vertical dimensions and compare the
differences between these dimensions with the dimensions
as shown in figure 2A-3 or 2A-4.
H orizontal Check
1 . Measure frame width at front and rear. If widths
correspond to specifications, draw centerline full length of
vehicle halfway between lines indicating front and rear
widths. If frame widths are not correct, layout centerline
as shown in Step 4.
2. Measure distance from centerline to corresponding
points on each side of frame layout over entire length.
Opposite side measurement should correspond within 3/
16".
3. Measure diagonals marked A, B and C. If the lengths
of intersecting diagonals are equal and these diagonals
intersect the centerline, frame area included between these
LIG H T T R U CK SERV ICE M ANUAL
Fig. 2A-1--Frame H orizontal C h eckin g-T ypical
points of measurement may be considered in alignment.
is no longer within limits, frame centerline may be drawn
through the intersection of any two previously drawn pairs
of equal, intersecting diagonals.
V ertical Check
from indicated points on the frame (figs. 2A-2 and 2A-4).
For example, if the tram bar is set at point B with a vertical
pointer length of 8-1/4 inches, and at point E with a vertical
pointer length of 5-1/4 inches (a height difference of 3
inches), the tram bar should be parallel with the frame. If
the area is twisted or misaligned in any way, tram bar will
not be parallel. Placing the tram bar vertical pointers on
opposite sides of the frame side rail is preferable in that
frame twist will show up during this vertical check. Figures
2A-2 and 2A-4 show typical checking points, with
dimensions for various frames shown in figure 2A-3.
Fram e Repair
Welding
drilled at the starting point of the crack to prevent
spreading. Widen V groove crack to allow complete weld
penetration.
4. If front or rear end of frame is damaged and width
Vertical dimensions are checked with a tramming bar
Before welding up a crack in frame, a hole should be