8-2
Published 01-14-2021 Control # 707-01
CARRIER
TMS9000-2 SERVICE MANUAL
FRONT AXLE
The carrier has two non-driving front steer axles. The front
axle centers are built of tempered seamless steel tube center
sections with heat treated steel forged knuckle pin ends.
The two front axles are bolted together with two walking
beams making a tandem axle assembly. Each axle is
mounted to brackets on the carrier frame and anchored
against forward, rearward, and side ways movement by
adjustable torque rods attached to the axles.
Suspension
The front axle suspension uses air bags and shock
absorbers to provide road shock cushioning. The air bags
are mounted on the saddle assembles, with the shock
absorber connected to both the saddle assemblies and the
carrier. The two saddle assemblies are connected at the
front by pivot blocks to carrier mounting brackets and at the
center of both walking beam assemblies.
Rubber bushings in the walking beam centers and ends, and
torque rod ends, restrict excessive movement but allows
enough movement to relieve stresses on metal parts. The
rubber joints allow a certain amount of in and out axle
movement which permits each axle to follow its own natural
course more closely through turns. Once a straight line is
resumed, the bushings square off the axle tandem so that
the leading tires set the tracking pattern. Torque rods along
with the walking beam creates a parallelogram style linkage
that assure positive axle alignment.
Air for the suspension system is controlled by a control valve
on the side console in the carrier cab and by two height
control valves mounted on each side of the carrier frame
next to the air bags . Each height c ontrol v alve is
mechanically actuated by a control lever attached to its
respective saddle assembly. The valve controls the amount
of air in each set of air bags thus controlling the height of the
frame. To deflate the entire air suspension system (front and
rear), position the SUSPENSION control valve on the carrier
cab side panel to DEFLATE. This causes the four height
control valves to shift and dump all air from the suspension
air bags. Four pressure switches sense the air pressure in
each set of air bags. Low air pressure in any of the four sets
of air bags will trip the respective pressure switch to
illuminate the DEFLATED indicator on the side console.
MAINTENANCE
General
Proper preventive maintenance will help control repair costs
and downtime. If a major overhaul is required, remove the
saddle assemblies and the tandem axle assembly from the
carrier. However, torque rods, air bags, shock absorbers,
walking beams, and other components can be removed
separately as required with the axles remaining on the
carrier. Refer to
, page 9-1 for specified
lubrication intervals. Check the torque on all bolts at least
once a year.
Beam Center Cap Fasteners
Periodically check the bolts on the saddle cap to prevent
wear of the walking beam center bushing into the saddle
assembly. Check bolt torque. Torque should be 310 to 375
Nm (228 to 276 lb-ft).
Beam End Connections and Bushings
Every 16,090 km (10,000 mi) check the torque of the beam
end bolts. Torque 615 to 815 Nm (453 to 601 lb-ft). Jack up
under each beam end and check for movement of the rubber
end bushing. Worn bushings will allow movement and the
bushings should be replaced. Periodically inspect the beam
for a lowering in the hanger and distorted or frayed rubber. A
gap on each side of the visible rubber at the lower end of the
end bushing is normal because the end bushings are in
compression.
Saddle Assembly End Cap Fasteners
Periodically check the bolt torque on the saddle assembly
end caps. Torque should be 310 to 375 Nm (228 to 276 lb-ft).
Beam Center Bushings
The beam center bushings control lateral movement of the
axles during cornering. Normal wear is evidenced by rubber
shredding from each end of the bushing. Worn bushings
result in increased lateral movement on turns, causing the
inside walls of the tires to rub on the suspension saddle
assemblies during turns. Replace the bushings before
serious tire damage results.
Beam Center Cross Tube
The center cross tube connects the two walking beams and
maintains axle alignment in turns. Inspect the cross tube for
damage and, if bent, it must be replaced. A bent tube will
result in axle misalignment and cause abnormal tire wear.
Fo
r
Reference
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