
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 4,800–16,000 service km
(3,000–10,000 service miles) 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, which includes school buses, 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
torque chartin this chapter. Regularly check the rear axle for damaged,
binding or worn parts.
NoSpin Detroit Locker positive locking differential
Vehicle 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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non-asbestos, fiberglass, mineral wool, aramid or carbon) may be a
potentially serious health hazard.
Avoid breathing brake lining fiber dust as it may be extremely
hazardous to your health. Always use of respirator during brake
maintenance.
Note:Persons handling brake linings should follow all precautions listed
below:
1. Always wear a respirator approved by the National Institute of
Occupational Studies of Health (NIOSH) or Mine Safety and Appliance
(MSA) during all brake service procedures. Wear the respirator from
removal of the wheels through assembly.
2.Neveruse compressed air or dry brushing to clean brake parts or
assemblies.
3. Clean brake parts and assemblies in open air. During assembly,
carefully place all parts on the floor to avoid getting dust in the air. Use
an industrial vacuum cleaner with a HEPA filter system to clean dust
from the brake drums, backing plates and other brake parts. After using
the vacuum, remove any remaining dust with a rag soaked in water and
wrung until nearly dry.
4.Neveruse compressed air or dry sweeping to clean the work area.
Use an industrial vacuum cleaner with a HEPA filter system and rags
soaked in water until wrung until nearly dry. Dispose of used rags with
care to avoid getting dust in the air. Use an approved respirator when
emptying vacuum cleaners and handling used rags.
5.Worker clean-up:Wash your hands before eating, drinking or
smoking. Vacuum your work clothes after use and then launder them
separately, without shaking them, to prevent fiber dust getting into the
air.
Air brakes - inspection and adjustment
A regular schedule for periodic cleaning, lubrication, adjustment and
inspection should be established based on the type of vehicle operation.
It is difficult to predetermine an exact maintenance interval (time or
mileage), since vehicles will be used in a wide variety of applications and
conditions. If you are uncertain of the proper schedule and procedures
for your vehicle, contact your dealer.
Periodic checking of push rod travel or brake adjustment is essential for
effective braking. Push rod travel should be checked every service
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Hydraulic brakes - fluid precautions
The Hydro-Max brake system consists of two completely separate
hydraulic systems operating with two different and incompatible fluids;
power steering fluid and hydraulic brake fluid. Failure to observe
precautions preventing the contamination of either system with fluid
from the other will result in swelling and deterioration of rubber parts
leading to reduced brake performance and eventual brake failure.
To avoid fluid contamination, the following should always be observed:
1. Use only fluids specified (or equivalent) and properly identified.
2. Add fluids only to the following locations:
•Power steering fluid to the power steering fluid pump reservoir
•Brake fluid to the brake master cylinder
Hydraulic brakes - brake lines, hoses and fittings
Inspect these components every 6,000 km (4,000 miles).
•Check lines for kinks, dents, corrosion or rupture.
•Check hoses for abrasions, kinks, soft spots or rupture, collapse,
cracks, twists or loose frame supports. When replacing a hose, be sure
there is adequate clearance to the hose to avoid an abrasion to the
new hose.
•Examine all connections for leaks.
•Repair or replace brake line tubes, hoses or fittings as required.
Driveline parking brake
Parking brake adjustment should only be performed by a qualified
technician, and in accordance with the instructions in the service
manual.
Use wheel chocks and exercise caution when inspecting under
the vehicle. A vehicle roll-away could result in property damage,
personal injury or death.
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Driving style—good driving and fuel economy habits
Give consideration to the lists that follow and you may be able to change
a number of variables and improve your fuel economy.
Habits
•Smooth, moderate operation can yield up to 10% savings in fuel.
•Steady speeds without stopping will usually give the best fuel
economy.
•Anticipate stopping; slowing down may eliminate the need to stop.
•Sudden or hard accelerations may reduce fuel economy.
•Slow down gradually.
•Driving at reasonable speeds (traveling at 88 km/h [55 mph] uses 15%
less fuel than traveling at 105 km/h [65 mph]).
•Using the air conditioner or defroster may reduce fuel economy.
•Resting your foot on the brake pedal while driving may reduce fuel
economy.
Conditions
•Carrying unnecessary weight may reduce fuel economy.
•Fuel economy may decrease with lower temperatures during the first
12–16 km (8–10 miles) of driving.
•Flat terrain driving improves fuel economy over hilly roads.
•Transmissions give their best fuel economy when operated in the top
cruise gear and with steady pressure on the accelerator.
•Close windows for highway driving.
NOISE EMISSIONS–EXTERIOR
In order to comply with the federal exterior noise regulations, your
vehicle may be equipped with noise emission items. Depending on the
vehicle configuration, it may have all or some of the following items:
Air Intake System
•Air Cleaner:should be inspected and its location should not be
altered. Do not alter inlet and outlet piping.
Body
•Wheel Well:splash shields, cab shields and under-hood insulation
should be inspected for deterioration, dislocation, and orientation.
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•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
1,600 km (1,000 miles) or six months, whichever comes first, the
U-Bolt nuts must be re-torqued. The U-Bolt nuts thereafter must be
re-torqued every 58,000 km (36,000 miles). The U-Bolt and nut
threads and seats should be cleaned and lubricated to assure 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 (floor jack preferred) 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.
FRAME AND TOW HOOKS
Your vehicles chassis is manufactured with frame rails of either mild
carbon steel, or HSLA steel. Each must be handled in a specific manner
to assure maximum service life. Before attempting frame repair or
modification, consult the service manual or your dealer.
It is important, particularly on vehicles where the tow hooks are used
frequently to inspect the front and rear tow hooks for damage or a loose
mounting.
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6. Clean and install the drain plug securely.
7. Add enough lubricant through the filler plug opening so that the
lubricant level is up to the bottom of the opening.
8. Clean and install the filler plug securely.
WHEELS
General
Wheel bearings should be inspected, lubricated and adjusted at regular
intervals. This is especially important if operating in deep sand, mud, or
water. Refer toLubricant specificationsin this chapter.
Oil lubricated front wheel bearings
During normal vehicle duty cycle, the lube and air inside the hub/wheel
cavity expands and if not vented, causes pressure build-up that could
cause accelerated seal wear.
There are two venting methods:
•a slit or small hole in the rubber check vent or
•the window
You can use either of these methods to prevent pressure build-up.
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.
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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.
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.
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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
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.
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