Chevrolet Light Duty Truck 1973 Service Manual page 169

Description 10-30 Series Truck
M aintenance...................................
Frame Alignment.....................
Horizontal C heck...................
Vertical Check.........................
Light duty 10-30 Series frames are of the ladder channel
section riveted type.
Figure 1 illustrates typical light duty frames with
crossmembers, body mounts and suspension attaching
brackets. This section also included general instructions
for checking frame alignment and recommendations on
frame repair.
UNDERBODY AND FRAME
INSPECTION
UNDERBODY INSPECTION
Raise the vehicle on a hoist (preferably a twin-post type).
Check for obvious floor pan deterioration.
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 might be required before the final
cleaning and protective treatment is performed.
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 ALIGNMENT
Horizontal frame checking can be made with tramming
gauges applied directly to the frame or by transferring
selected points of measurement from the frame to the
floor by means of a plum bob and using the floor layout
for measuring. Figure 2 may be used as a general guide
in the selection of checking points; however, selection of
these points is arbitrary depending on accessibility and
convenience. An important point to remember is that for
each point selected on one side of the frame, a
corresponding point on the opposite side of the frame
SECTION 2
FRAME
INDEX
.2-1 Frame Repair......................................................................2-2
.2-1 W elding...............................................................................2-2
.2-1 Bolting..................................................................................2-2
.2-2 Underbody A lignm ent.....................................................2-2
2-2
.
DESCRIPTION
The G-Van frame side rails, cross sills and outriggers are
part of the underbody assembly which is a welded unit.
Misalignment of the underbody can affect door opening
fits and also influence the suspension system, causing
suspension misalignment. It is essential, therefore, that
underbody alignment be exact to within - 1/16" of the
specified dimensions.
M AINTENANCE
must be used for vertical checks, opposite and alternate
sides for horizontal checks.
Vehicle Preparation
Points to remember when preparing vehicle for frame
checking:
1. Place vehicle on a level surface.
2. Inspect damaged areas for obvious frame misalign­
ment to eliminate unnecessary measuring.
3. Support vehicle so that frame sidemembers are
parallel to the ground.
Tramming Sequence
1. Dimensions to bolts and/or holes in frame extend
to dead center of the hole or bolt.
Fig. 1 - 1 0 - 3 0 Series Frame—Typical
LIGHT DUTY TRUCK SERVICE MANUAL