GMC 4000 Series Service Manual page 38

Subject
Cab Description
Cab M o u n tin g s................................................................
S e a t s .................................................................................
Doors
Cab Replacement
Heating and Ventilation
glass, and windshield wipers which is common to all types
of cabs is explained at beginning of this group in "GENERAL
MAINTENANCE" section.
SHEET METAL (SEC. 11) of this manual.
The basic conventional cab is of all steel
welded construction (fig. 1). Cab side construction
consists of a one-piece body door opening frame
which assures more positive sealing around the
door when closed.
The one-piece roof panel has longitudinal
ribbing to stiffen and reinforce the roof. The floor
panel, also of one-piece construction eliminates
joints, pockets and seams which normally act as
moisture traps. In most cases, all paneling pieces
are lap-jointed and welded for maximum in sealing
and structural strength.
Front outside air intake is located at top cen­
ter of cowl. Opening and closing of intake is con­
trolled by push-pull lever at top of dash panel.
Outside air for the heating system enters through
a separate louvered opening at right side of cowl.
Doors are of double-wall construction. Lower
inner panel of door has a cut-out allowing access
to door control mechanism for adjustment and
parts replacement. Horizontal slots in door hinge
assembly provides for adjustment of door in cab
opening. Door vent window is of friction-type with
positive theft-resistant latch.
The windshield used on all conventional cab
models covered in this manual is of the one-piece
type.
CAB MOUNTINGS
Four point type cab mountings are used on
these vehicles. The front mount consists of an
upper and lower cushion assembly as shown in
figure 2. Cab rear mounts are of the compression
type (fig. 3), utilizing rubber biscuit cushions. This
compression-type mounting is readily replaced by
G M C S E R V I C E M A N U A L
Go-twesitiosial Gab
Contents of this section are listed in Index below:
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NOTE: Maintenance information on painting, windshield
Information on sheet metal components is covered in
CAB DESCRIPTION
Page No.
31
31
32
32
43
43
removing one mounting bolt.
At regular intervals, all cab mountings should
be checked for loose attaching parts and for de­
teriorated or collapsed rubber cushions.
Any one cab mounting can be readily replaced
after removing the weight of cab at that particular
mounting.
IMPORTANT: Raise cab only to height n eces­
sary to replace mounting components. If cab is
raised too high, damage to vehicle operating con­
trols, wiring and lines may occur. Before lowering
cab, be sure cushion is properly centered between
frame and cab.
Figure 1 — C a b W e ld e d Construction
Sec. 1
Page 31