GMC 4000 Series Service Manual page 71

Sec. 1
Page 64
TILT CAB
frame bracket. Remove arm from bar and bracket.
5. Loosen cap screw which clamps cab right
mounting -bracket to right end of torsion bar.
6. Slide torsion bar from cab right frame
bracket, then slide bar in opposite direction from
cab left support.
CAUTION: DO NOT hammer on end of bar.
INSTALLATION
1. Before replacement of torsion bar, inspect
frame brackets (castings) and cab supports (cast­
ings) for cracks. DO NOT WELD OR BRAZE
BRACKETS. If cracked, replace.
2. Prelubricate left frame bracket opening and
right frame bracket. Slide hex end of torsion bar
into left frame bracket, then insert opposite end
into cab right support.
3. Install torsion bar anchor lever over end of
bar and into frame bracket.
NOTE: Lever should be located on bar so that
opposite end of anchor lever is located near center
of serrations on cab bracket (fig. 33).
4. Install cab stop brackets (if previously re­
moved) to torsion bar cab and frame brackets as
shown in figure 34. Torque attaching bolts to 35 to
50 foot-pounds. Make sure stop brackets are in­
stalled as shown.
5. Install torsion bar right frame bracket cap
and cab left support cap with two bolts and wash­
ers. Torque bolts to 50-60 foot-pounds.
6. Tighten bolt which clamps cab right mount­
ing bracket to end of torsion bar (fig. 34) to 65-75
foot-pounds.
7. Lubricate all cab tilt lubrication fittings
with lubricant specified in LUBRICATION (SEC. 0).
8. Raise and lower cab to check operation. If
cab rises too fast from operating position or if
considerable effort is required to raise cab, make
torsion bar tension adjustment as directed under
"Torsion Bar Tension Adjustment."
G M C S E R V I C E M A N U A L
Figure 3 4 — C ab Torsion Bar Stop Brackets Installed
torsional load is removed from torsion bar. Usually
the bar will become unloaded when cab is tilted
45 to 50 degrees. This unloaded angle position
may vary slightly on different vehicles.
ness of screw which clamps cab right mounting
bracket to torsion bar. Tighten screw firmly ONLY
when torsion bar is unloaded - cab tilted part way.
If screw is loose, cab bracket may fracture when
torsion bar is loaded.
sion bar becomes unloaded. An overhead hoist is
recommended for supporting cab in this position
as it will allow cab to tilt slightly fore or aft to
facilitate alignment of torsion bar anchor lever to
cab frame bracket.
lever and serrated spacer block to the cab frame
bracket (fig. 33). Loosen nut only enough for spacer
to clear serrations.
sm all serrated spacer block can be relocated to
new related serrations on cab frame bracket as
desired.
position anchor point of torsion bar anchor lever
as directed above.
rapidly to full-tilt position, damage to cab check
link could occur and also upon lowering of the cab
to operating position, considerable effort may be
required.
lever bolt nut.
C a b Su p p o rt
Bracket
Stop Bracket
Fram e Bracket
R IG H T M O U N T I N G
TORSION BAR TENSION
ADJUSTMENT
1. Tilt cab forward to an angle whereby the
IMPORTANT: Before continuing, check tight­
2. SAFELY support cab at angle at which tor­
3. Loosen nut on bolt which attaches the anchor
4. By tilting cab slightly fore and aft, the
5. Tighten anchor bolt nut to 80-90 foot-pounds.
6. Check cab tilting action. If necessary, re­
NOTE: If adjustment is such that cab rises
IMPORTANT: Final check tightness of anchor
Torsio n B a r
C la m p Bolt—
T o rq u e To
6 5 To 7 5 Ft.-Lbs.
T-3420