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2A-2
1977
PONTIAC SERVICE MANUAL
Fig.
2A-1 Frame
Identification
ON CAR SERVICE
FRAME INSPECTION
1. Raise car on a hoist (preferably a twin-post type).
2. Check for obvious floor pan deterioration.
3. Check for loose dirt and rust around the inside of the
frame rails, on top and at the ends where corrosion may exist
in hidden areas. Check especially in the frame box sections
for accumulation of debris.
UNDERBODY INSPECTION
1. Raise car on a hoist (preferably a twin-post type).
2. Check for obvious floor pan deterioration.
3. Check for loose dirt and rust around the inside of the
floor pan reinforcement member access holes. This is the first
indication that corrosion may exist in hidden areas, and that
repairs may be required before the final cleaning and
protective treatment is performed.
4. Using a chisel, ensure that the drain provisions in the
floor pan reinforcement members are open. There are drain
holes in the body side panels also. These holes can be opened
by using a punch or drift. The side panel drain holes are in
the rear section of the rocker panels, and in the lower rear
quarter panels.
FRAME REPAIR
Frame Alignment
Vehicles involved in an accident of any nature which
might result in a "bent" or "sprung" frame should always be
checked for proper frame alignment in addition to steering
geometry and wheel alignment. Fig. 2A-2 can be used to
check the alignment of a frame that has been distorted. The
reference points indicated are to be checked with a tram
gauge. The dimensions between the various reference points
will show where straightening operations are necessary.
Corresponding measurements must be equal within 1/4 inch.
1. Measure X-X. If not equal, frame horn or front
suspension crossmember is misaligned.
2. Measure Y-Y. If not equal, center portion of frame
is misaligned.
3. Measure Z-Z. If not equal, rear end of frame is
misaligned.
Tramming Sequence
When checking a frame for alignment in case of damage,
the first step is horizontal
"X"
checking with a tram gauge
as indicated above. Frame alignment checks on all models
should be made with the tram gauge points set at the center
of each locating point indicated and the cross bar level to
insure accuracy.
If a tram gauge is not available, the "plumb bob" method
of checking may be used. To assure any degree of accuracy
when using this method, the car should be on a level floor.
By using this method, it is only necessary to have a piece
of cord attached to an ordinary surveyor's plumb bob. When
measuring the distance between two points, the free end of
the cord should be placed on the reference point allowing the
plumb bob to hang to the floor. A check mark should be made
on the floor just under the tip of the plumb bob. This
operation should then be repeated at all reference points.
With these points located on the floor, they may be easily
measured with a rule.
The second step is checking the vertical dimensions from
the datum plane to the points to be trammed. With the proper
settings, the tram bar will be on a plane parallel to that of
the frame. The exception to this would be when one of the
reference locations is included in the misaligned area; then
the parallel plane between the frame and the tram bar may
not prevail. After completion of the repairs, the tram gauge
should be set at the specified dimension to check the accuracy
of the repair operation.
Frame Dimensions
Frame dimensions for A, B and G Series are shown in
Figs. 2A-3 and 2A-4.
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