Check to make sure that the axle mounting U-bolt nuts, attaching or
mounting bolts and nuts are securely tightened. Regularly check front
axle for damage, binding, worn parts and adequate lubrication.
At regular intervals, or during other scheduled maintenance, (tire
rotation/service, wheel bearing service, alignment, etc.) the kingpins
should be checked for excessive wear. Refer to the service manual for
proper procedures.
Toe-in setting - general inspection
Inspecting steer axle tires in the first 3,000–10,000 service miles
(4,800–16,000 service km) will generally show if tires are wearing
normally.
Rapid outside shoulder wear on both tires indicates too much toe-in.
Rapid inside shoulder wear on both tires indicates too much toe-out. In
P&D-type service, left-to-right steer tire tread life differentials up to 40%
can be observed depending on routes and other variables.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, load range (ply rating) and steer axle loading typical for
their operation (each steer axle tire will equal
1 2steer axle loading).
Special applications may warrant a setting based on past experience with
the type of tire operating loads and conditions. Radial tires are more
sensitive to toe-in setting than bias ply tires. While not insensitive to
vehicle alignment, fine tuning school bus alignment to line-haul truck
standards will not drastically improve tire tread life.
It is essential that correct toe-in and tire pressure be maintained for
optimum tire wear.
Rear axle - general inspection
Check to make sure that the axle mounting U-bolts, attaching or
mounting bolts and nuts are securely tightened. Refer toU-bolt nut
torquein this chapter. Regularly check the rear axle for damaged,
binding or worn parts.
NoSpin Detroit Locker positive locking differential
Vehicles equipped with this type differential have the operator’s manual
supplied with the vehicle. Refer to this manual for maintenance checks.
Brake system - general inspection
Your vehicle is equipped with non-asbestos brake linings. However,
exposure to excessive amounts of brake material (whether asbestos or
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Verify drive axle air suspension height and height control valve
performance at engine lube oil change intervals.
Periodically:
•Check condition of spring leaves for evidence of fatigue, bending or
breakage.
•Check condition of suspension mounting brackets and bushings.
•Check that torque rod mounting fasteners are tight.
•Check to be sure the suspension alignment is maintained at all time.
•Check U-bolts after the chassis has been operating under load for
1,000 miles (1,600 km) or six months, whichever comes first, the
U-Bolt nuts must be re-torqued. The U-Bolt nuts thereafter must be
re-torqued every 36,000 miles (58,000 km). The U-Bolt and nut
threads and seats should be cleaned and lubricated to ensure a “like
new” condition when re-torquing.
Note:See theU-Bolt Nut Torquechart later in this section.
Supporting your vehicle for service
When performing service repairs on your vehicle, first prepare the
vehicle by doing the following:
1. Park the vehicle on a level concrete floor.
2. Set the parking brake and block the wheels to prevent the vehicle
from moving.
3. Select a jack with a rated capacity sufficient to lift and hold up the
vehicle.
4. Raise the vehicle with the jack applied to the axle(s). DO NOT use the
bumper as a lifting point.
5. Support the vehicle with floor stands under the axle(s). If the axle or
the suspension are being serviced, support the vehicle with floor stands
under the frame side-members, preferably between the axles.
Do not use a jack when working under a vehicle. It may give
way, causing the vehicle to fall and result in property damage,
personal injury or death. Always use floor stands to support the
vehicle.
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Normal maintenance
Over a period of time, if not routinely cleaned, a slight film of oil can
collect dirt around the rubber fill plug and face, which could appear to
be a leak. Routine cleaning ensures that the lube level can be easily
observed through the clear window as intended. In situations where the
window is clean on the outside but discolored on the inside, the lube
level may be checked by inserting a finger through the rubber check
vent hole.
The specified lube level for a clear window type hubcaps is from the
minimum line to + 5/16 inch above the minimum line.
If the lube level should suddenly drop dramatically below the minimum
level, see the Service Manual for diagnostic procedure.
Installation, tightening and alignment
8–lug wheel
10–lug wheel
When installing wheels, be certain that the threads on studs and nuts are
clean to permit correct torquing of nuts. The mounting surfaces of rims,
wheels, spacer rings and clamps must be free of dirt, rust, lubricants or
damage.
Use a wire brush to clean the mounting contact surfaces. Do not use
lubricant on threads.
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After the rim or wheel has been properly tightened, it should be checked
for alignment. Rotate the wheel with a piece of chalk attached to a
steady, firm surface, and placed to just barely clear the outside surface of
the tire bead seat. This procedure will point out the high spot. A high
spot does not necessarily mean that the lug nuts have been unevenly
tightened. This condition or misalignment could be caused by a bent
wheel.
Checking the alignment of the wheel/rim installation is more important
on cast spoke rims since the rims can be drawn out of alignment when
improperly tightened. Use the following installation procedures.
Disc wheel with flange nuts (hub-piloted)
Front wheel mounting of flange nut
system
1. Flange nut
2. Wheel(s)
3. Brake drum
4. Wheel stud (22 mm)
5. Wheel hub
Rear wheel mounting of flange nut
system
1. Flange nut
2. Wheel(s)
3. Brake drum
4. Wheel stud (22 mm)
5. Wheel hub
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1. Slide inner rear or front tire and wheel in position over studs and push
it back as far as possible. Use care so that the threads on studs are not
damaged.
2. Position the outer rear tire and wheel in place over the studs and
push it back as far as possible. Use care so that the threads on studs are
not damaged.
3. Run the nuts on the studs until they contact the wheel(s). Rotate the
wheel assembly a half-turn to permit the parts to seat.
4. Draw up the nuts alternately following the crisscross sequence
illustrated underInstallation, tightening and alignment. Do not fully
tighten the nuts. This will allow uniform seating of the nuts and ensure
even face-to-face contact of the wheel and hub.
5. Continue tightening the nuts to the torque specifications in the torque
chart using the same crisscross sequence shown.
6. After operating the vehicle approximately 50 miles (80 km), check the
nuts for tightness. Some natural seating of parts may be encountered
and the torque on the nuts will drop. Retighten all nuts to specifications.
Once a week, inspect and retighten the wheel stud nuts.
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Maintenance Operation Frequency - Observation
Inspect the automatic slack
adjuster functionInsufficient power shown in loaded
practice stop.
Check the operation of the
brakes, the clutch, and the
steering
(1),(2)
Vehicle handling qualities not up to
par.
Inspect the vehicle for missing,
damaged, or mislocated noise
shieldsExcessive noise emanates from under
the cab or engine compartment.
Check the engine performance
and the engine governorExcessive engine noise.
Inspect the fan, the fan shroud,
and the fan clutchEngine overheats, fans runs at high
speed constantly, excessive fan noise,
or fan wobble due to worn bearings.
Check for operation of ABS
warning lampAt each engine start up.
Inspect the entire exhaust
system (including inlet pipe,
muffler, outlet pipe and all
exhaust clamps and fasteners)
for holes, leakage, breakage,
looseness and corrosive
damageExcessive noise or the smell of fumes
is experienced.
Inspect the engine air
induction system (including the
air ducts and the air filter) for
loose fitting, damaged or
missing componentsExcessive noise emanates from the
engine compartment.
Inspect the tires and check the
air pressure
(3)Poor steering, wandering or excessive
tire wear.
Balance the wheels and the
tiresVibration or abnormal tire wear
indicates imbalance.
Check the front end alignment
(3)Poor steering, wandering or excessive
tire wear.
Check the transmission and
engine mountings
(2)Hard shifting or excessive vibration.
Check and adjust transmission
controls
(2)High effort to shift or noisy
transmission.
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Maintenance Operation Frequency - Observation
Check fuel pump pressure Insufficient full-throttle power or
backfiring.
Clean radiator cap seal. Clean
and inspect the cap surface on
the radiatorWhen the cap does not hold pressure.
Check the battery terminals for
corrosionWhenever electrical power supply has
diminished.
Tighten the wheel mounting
nuts to the specified torque.
Refer toServicing your
wheels and tiresin the
Maintenance and
SpecificationschapterRequired initially at 500 and 1000
miles (800 and 1600 km). Perform
again at 500 and 1000 mile (800 and
1600 km) intervals after each tire
removal/replacement.
Clean body/door drain holes At least twice annually.
Clean windshield wiper blades As required.
Replace windshield wiper
bladesIf wiping the blades with a clean cloth
and mild detergent and washing with
a cleaner does not restore a clean
wipe.
Lubricate body lock cylinders Noisy or difficult to operate.
Check headlamp alignment Lamp beams in wrong position when
vehicle operating loaded.
Check windshield washer fluid
level; add fluid if requiredIf washes do not spray when operated.
1- During maintenance and repair, protect the fuel tube and the hose
assemblies, the power steering lines, and the brake lines from the
external heat, the acids and the abrasion that could damage the lines.
2- Check for (free) linkage action and ensure that (return) spring
force is adequate to maintain pedal free play.
3- Adjust, repair or replace as required with the same or equivalent
parts.
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