GMC 1982 Light Duty Truck Service Manual page 144

2 A -2 FRAME
E rror will result if a tram bar is not level and centered
at the reference points.
4. O btain vertical dimensions and com pare the differences
betw een these dim ensions w ith the dim ensions as
shown in Fig. 2A-3 or 2A-4.
Horizontal Check
1. M easure fram e width at front and rear. If widths
correspond to specifications, draw centerline full length
of vehicle halfw ay between lines indicating front and
rear widths. If fram e widths are not correct, layout
centerline as shown in S tep 4.
2. M easure d istan ce from cen terlin e to corresponding
points on each side of fram e layout over entire length.
Opposite side m easurem ent should correspond within
3/16 in. (4.7 mm).
3. M easure diagonals m arked A, B and C. If the lengths
of intersecting diagonals are equal and these diagonals
intersect the centerline, fram e area included between
these points of m easurem ent may be considered in
alignm ent.
4. If front or rear end of fram e is dam aged and width is no
longer within limits, fram e centerline m ay be drawn
through the intersection of any two previously drawn
pairs of equal, intersecting diagonals.
V ertical Check
from indicated points on the fram e (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 in. (206 m m ), and a t point E with a
vertical pointer length of 5-1/4 in. (131 m m ) (a height
difference of 3 in. (75 m m ), the tram bar should be parallel
with the fram e. If the area is twisted or m isaligned in any
way, tram bar will not be parallel. Placing the tram bar
vertical pointers on opposite sides of the fram e side rail is
preferable in th at fram e tw ist will show up during this
vertical check. Fig. 2A-2 and 2A-4 show typical checking
points, with dimensions for various fram es shown in Fig. 2A-
3.
Fram e Repair
W eld ing
drilled at the starting point of the crack to prevent spread­
ing. W iden V groove crack to allow com plete weld
penetration.
Fig. 2A-1--Frame Horizontal Checking-Typical
V ertical dimensions are checked with a tram m ing bar
Before welding up a crack in fram e, a hole should be
NOTICE: Do not weld into corners of fram e or along
edges of side rail flanges. W elding at these points will
tend to weaken the fram e and encourage new cracks.