GMC 1976 ZEO 6083 Maintenance Manual page 126

2- 2 FRAME
FRAME ALIGNMENT
The most convenient way to check frame align-
ment is to select various corresponding points of
measurement on the outside of each side rail and
then, by use of a plumb bob, transfer these points to
a layout on a level floor . (Note: Flange width may
vary and should not be used as a reference point.)
Since the frame is basically made of three differ-
ent sections, the procedure for checking the frame is
as follows:
CHECKING ALIGNMENT
The diagram shown in Figure 2 can be used to
check the alignment of a vehicle frame that has been
distorted.
Corresponding measurements must be equal within
1/4" .
1 . Measure A-B. If not equal, front end of frame
is misaligned .
2 . Measure B-C. If not equal, center portion of
frame is misaligned .
3 . Measure C-D. If not equal, then rear suspen-
sion crossmember is misaligned .
FRAME REPAIR
In case of collision, frame members can often be
satisfactorily straightened to the required limits .
However, the front suspension crossmember is made
to unusually close limits necessary for proper front
wheel alignment; therefore, straighetning of this unit
may not be successful .
Figure 2-Frame Alignment
It is possible that the ordinary straightening
methods will suffice for minor damage to the front
suspension crossme ber; however, in case of serious
damage or fracture, the entire front suspension cross-
member or front frame extension must be replaced .
Before the member is replaced, it is essential that the
frame alignment be checked, and corrected if neces-
sary .
Finished bolts snugly fitted in reamed holes
should be used . The nuts should be securely tight-
ened and lockwashers used, care being taken that
washers do not spread .
FRAME MATERIAL
The frame material is 950-1023-1080 steel. The
frame may be welded if necessary using electrodes
noted in table 1 .
NOTE :
It is NOT recommended that the frame
be welded to repair alignment If there is sub-
stantial frame damage - from collisions, etc. -
replacement of major components is recom-
mended .
ELECTRODE USAGE WITH FRAME
MATERIAL
Material ... . .... . ... . . ... . . .. . . . .. . . ... . . . .. . . ... . . .. 1023-950 steel
Type or Electrode . . . ... . . .. . . ... . . . .. . . ... E6013 or E7018
REPLACING FRAME EXTENSION
The purpose of this section is to enable a techni-
cian to change a front or rear frame extension due to
extensive damage from a collision, etc . It is not
recommended that this procedure be used until it is