GMC 4000 Series Service Manual page 58

Figure 4 — A p p ly in g Insulation
Interconnected with the cab front mountings is
a torsion bar (fig. 3) which is under load when cab
is in either the operating or full-tilted position.
Right end of bar is anchored to cab bracket and
left end is anchored by lever to frame bracket as
shown in figure 3. Bar is unloaded when cab is
tilted approximately 45 degrees, therefore, torsion
bar a ssists operator in both the raising and lower­
ing of cab.
CAUTION: UNDER
STANCES SHOULD THE BOLTS WHICH
ATTACH TORSION BAR RIGHT ANCHOR
B R A C K E T TO C A B AND THE TORSION
BAR L E F T ANCHOR L E V E R TO F R A M E
BE LOOSENED OR R EM O V ED WHEN CAB
IS IN O PERA TING OR F U L L T IL T POSI­
TIONS WHICH IS WHEN BAR IS LOADED.
AN INJURY COULD
ANCHOR B R A C K E T AND TORSION BAR
IS ALLO W ED TO REL EA SE .
Attaching bolts can be removed safely when
bar is unloaded, cab tilted part way (approx. 45
degrees). Normally it should never be necessary
to remove bolts. Whenever torsion bar is inoper­
ative, cab must be supported safely.
Attaching bolts at front pivot mountings should
be checked at regular intervals for tightness. Loose
mountings will allow shifting of cab and eventual
failure of other items connecting cab to chassis.
Front pivot mountings have fittings for lubrication
purposes. Lubricate as directed under LUBRICA­
TION (SEC. 0) of this manual.
Rear mounting has positive locking mechan­
ism to retain cab in normal operating position in
relation to chassis frame. The rear mounting also
includes an additional safety catch. Tightness of
cab hold-down lock can be adjusted by shortening
or lengthening catch release rod. After adjusting
G M C S E R V I C E M A N U A L
NO C IR C U M ­
RESULT WHEN
.j Four A tta ch in g Studs
/ (Stud N u ts A cce ssible
from U nd e r C ab)
Figure 5 — Driver's Seat M ounting and Adjustment
rod, tighten end yoke lock nut. Cab hold-down catch
shaft is equipped with a lubrication fitting.
A check link is provided near the right front
mounting (see inset, fig. 2) which lim its the dis­
tance cab can be tilted forward and automatically
locks the cab in the full-tilt position. Check link
must be released before cab can be returned to
normal operating position.
INSULATION
Insulation, applied to cab understructure di­
rectly over engine, is highly resistant to abrasion
and corrosion and is designed to give maximum
sound deadening and insulation.
In the event a repair such as welding is re­
quired to that part of cab covered with insulation,
it is first necessary to remove the insulation from
that area. After completing repair, insulation se c ­
tions can be cut to size and cemented over the re­
paired area (fig. 4). Be sure to clean area thor­
oughly before installing new section of insulation.
SEATS
SEAT ADJUSTMENT (Fig. 5)
Driver's seat is provided with "fore"and "aft"
adjustment only. Pull out on lever at left side of
seat to disengage seat position lock.
SEAT TRACK REPLACEMENT (Fig. 5)
1. Tilt cab forward, then remove four nuts
and washers from studs which attach seat tracks
to seat riser of cab.
2. Lower cab to operating position, then lift
seat assembly from cab.
3. Remove four nuts which attach each track
assembly to seat assembly and remove track.
4. Reverse the above procedure to install
track assembly.
Sec. 1
Page 51
TILT CAB