GMC 4000 Series Service Manual page 74

of nuts at top of sill, tapped plate, as shown in
figure 2 can be used.
4. Insert a block of hard, dry wood (with grain
running up and down) in channel of frame at each
mounting. Block must be of sufficient length to ex­
tend well under clip plates. Thickness of block
should extend beyond width of frame flanges to
permit grooving the blocks. Inner mounting bolt
will fit into groove and hold block firmly in place
(fig. 1 or 2).
5. If shoulder on bolt head is square, as on
carriage bolts, the holes in upper clip plates should
also be square. Shoulder of bolts should be driven
into holes to prevent bolts turning. If U-bolts are
used, bolt must be of "flatted" type as shown in
figure 2. A clip or spreader must be used on each
U-bolt, and bolt must not be used in reverse of
position shown in figure 2.
6. Use two nuts on threaded end of each bolt.
Tighten inner nut firmly, then tighten outer (lock)
nut firmly against inner nut. DO NOT USE SINGLE
NUT AND LOCK WASHER. However, lock washer
should be used with tapped plate type of mounting.
CROSS SILL M O UNTING
If body is not equipped with longitudinal sills,
attach s ills , if possible, as shown in figure 3,
since mounting on cross s ills (bolsters) is not
recommended. Longitudinal sills can be easily
made of dry hardwood and attached to either wood
or metal cross sills by means of angle irons and
bolts. General practice of body mounting is on
longitudinal sills; however, where the conditions
necessitate mounting directly on cross s ills , the
following practices should be observed:
1. Sills must rest squarely on frame top
flange. Countersink sill, if necessary, to clear
rivet heads - - d o not use spacer.
2. Use same type of mounting bolts and clip
plates as described in ''Mounting Bolts." The num­
ber of clips to use is of course dependent upon
G M C S E R V I C E M A N U A L
Figure 3 — M ethod of Attaching Longitudinal Sills to Body
load, body style, etc. Carriage or step bolts are
useful in this type mounting, since bolt heads pro­
ject above floor.
ever mountings are used on frame. Mount clip
plates diagonally across frame rail - - with one
bolt forward of cross sill and inside frame rail
and other bolt to rear of cross sill and outside
frame rail.
mounting since mounting bolts, of necessity, pro­
ject through floor or platform of body. Make sure
that heads of bolts are well supported at body floor
with plates or washers.
BODY M OUNTINGS
3. Use wood blocks in frame channel when­
4. U-bolts cannot be used with this type of
Sec. 1
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