If the steering wanders or pulls, check for:
•Underinflated tire(s) on any wheel(s)
•Uneven vehicle loading
•High crown in center of road
•High crosswinds
•Wheels out of alignment
•Loose or worn suspension components.
AIR SUSPENSION (IF EQUIPPED)
Note:Do not operate your vehicle without air in the suspension springs.
Operating your vehicle without air in the suspension springs damages the
suspension, degrades ride performance and may cause property damage.
The air suspension system automatically adjusts to different loads to
maintain a constant frame height, allows for ease of vehicle loading,
provides improved vehicle ride, and increased driver comfort.
Air Suspension Dump Switch
Note:The suspension dumps air when the ignition is in the accessory or
on position, but fills only when the ignition is in the on position.
A switch located in the overhead
switch pack controls the system. It
operates only when the ignition is in
the accessory or on position and the
air tanks have sufficient pressure to
fill the air springs. When you turn
off the ignition, the suspension
remains in whatever state it was last
set.
Pressing the lower portion of the switch exhausts air from the air
springs, lowering the frame for loading. Pressing the upper portion of the
switch fills the air springs so your vehicle remains at normal ride height.
System Indicator Light
The air suspension indicator light illuminates when using the
switch to release air pressure in the rear air shocks. Never
drive your vehicle when the warning lamp is illuminated and
there is low (or no) air pressure in the shocks.
CK
SUSP
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BREAKING-IN
You need to break in new tires for approximately 300 miles
(480 kilometers). During this time, your vehicle may exhibit some unique
driving characteristics. Avoid driving too fast during the first 1000 miles
(1600 kilometers). Vary your speed frequently and change up through
the gears early. Do not labor the engine.
ECONOMICAL DRIVING
Several things affect your vehicle’s fuel economy, such as how you drive,
the conditions you drive under and how you maintain your vehicle.
You may improve your vehicle’s fuel economy by keeping these things in
mind:
•Accelerate and slow down in a smooth, moderate fashion.
•Drive at steady speeds without stopping.
•Anticipate stops; slowing down may eliminate the need to stop.
•Close the windows for high-speed driving.
•Drive at reasonable speeds. Traveling at 55 mph (88 km/h) uses 15%
less fuel than traveling at 65 mph (105 km/h).
•Keep the tires properly inflated and use only the recommended size.
•Use the recommended engine oil.
•Perform all regularly scheduled maintenance.
You may want to avoid doing these things since they may reduce your
vehicle’s fuel economy:
•Sudden or hard accelerations.
•Warm up your vehicle on cold mornings.
•Use the air conditioner or front defroster.
•Use the speed control in hilly terrain.
•Rest your foot on the brake pedal while driving.
•Carry unnecessary weight. Approximately 1 mpg (0.4 km/L) is lost for
every 400 pounds (180 kilograms) of weight carried).
•Add particular accessories to your vehicle (such as bug deflectors,
roll bars and light bars, running boards, ski racks).
•Drive with the wheels out of alignment.
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Climate Control System
Have the air conditioning system checked each spring. The refrigerant
charge, cleanliness of the condenser-evaporator cores and belt condition
are essential to system performance.
When the air conditioning system is being used daily, remove the fresh
air filter (if equipped) once each season and check for things such as
dirt and lint. Replace the filter if necessary. Vehicles operating in
unusually dusty conditions may require more frequent filter inspection
and replacement.
Front Axle
Maintaining the front axle alignment to specifications is very important.
A qualified technician should check and maintain the alignment. Regular
inspections should include:
•Toe-in inspection and adjustment (if necessary), particularly with
radial tires.
•Checking for proper tightness of axle mounting U-bolt nuts, attaching
or mounting bolts and nuts.
•Checking the axle for damage, binding, worn parts and adequate
lubrication..
•Checking the kingpins for excessive wear. Also, perform this check
during other scheduled maintenance (such as tire rotation or service,
wheel bearing service and alignment). See the workshop manual for
proper procedures.
Toe-in
It is essential to maintain correct toe-in and tire pressure for optimum
tire wear.
Inspecting steer axle tires in the first 3000–10000 service miles
(5000–16000 service kilometers) generally shows 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, there can be a left-to-right steer tire tread life
differential up to 40% 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 equals
1 2steer axle loading).
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Periodically check:
•Condition of spring leaves for evidence of fatigue, bending or
breakage.
•Condition of suspension mounting brackets and bushings.
•Torque rod mounting fasteners for tightness.
•For proper suspension alignment. Maintain proper alignment at all
times.
•U-bolts. After the chassis has been operating under load for
1000 miles (1600 kilometers) or six months (whichever comes first),
the U-bolt nuts must be re-torqued. Re-torque the U-bolt nuts every
36000 miles (60000 kilometers) thereafter. Clean and lubricate the
U-bolt and nut threads and seats to make sure a like new condition
when re-torqueing.
Note:SeeSpring U-bolt checklater in this chapter.
Supporting Your Vehicle for Service
WARNING: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.
Prepare your vehicle for service repairs by doing the following:
1. Park your vehicle on a level, concrete floor.
2. Set the parking brake and block the wheels to prevent your vehicle
from moving.
3. Select a jack with a rated capacity sufficient to lift and hold up your
vehicle.
4. Raise your vehicle with the jack applied to the axle(s). Do not use
the bumper as a lifting point.
5. Support your vehicle with floor stands under the axle(s). When
servicing the axle or the suspension, support your vehicle with floor
stands under the frame side-members, preferably between the axles.
Frame and Tow Hooks
Your vehicle’s chassis is manufactured with frame rails of either HSLA
steel or heat-treated steel. Handle each in a specific manner to make
sure maximum service life. Consult the service manual or an authorized
dealer before attempting frame repair or modification.
It is important, particularly on vehicles that use tow hooks frequently, to
inspect the front and rear tow hooks for damage or a loose mounting.
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Irregular Wear:If irregular wear is present, check the axle alignment,
tire pressure, wheel balancing, shock and suspension component
condition, and wheel bearing end play.
This condition not only shortens tire life, but also adversely affects the
handling of your vehicle, which is dangerous.
Rotating tires from one wheel position to another is an often-used way to
even out many types of irregular wear or to avoid it altogether. Some of
the more effective tire rotation programs are:
•You can rotate steer tires that have developed some type of irregular
wear pattern to drive axles if using rib tires on all wheel positions.
Applying steer tires to a drive position often cleans them. You can
move them back to the steer axles or run out to re-tread stage on the
rear axle.
•Another rotation possibility for fleets with rib tires in all wheel
positions is to break in the new steer tires in the drive axle positions,
then move them to steer axles. This wears away tread rubber
relatively quickly in the early life of a tire when it is most likely to
develop an unusual wear pattern.
•You can place drive axle tires on the other end of the same axle to
reverse the direction of rotation. This is often helpful if a heel and
toe or alternate lug wear pattern has developed.
You can help minimize irregular wear by:
•Using the right inflation pressure for the load being carried.
•Maintaining proper front wheel alignment, especially toe-in, to
specifications.
•Maintaining proper tire and wheel balance.
•Maintaining shock absorbers and suspension components.
Use of Tire Chains
See the chain manufacturer’s recommendation for correct tire chain
usage, installation and removal.
WHEELS
General Information
Note:Remember to replace the wheel air valves when replacing the road
tires at the end of their useful lives.
Inspect, lubricate and adjust wheel bearings at regular intervals. This is
especially important if operating in deep sand, mud or water. See the
Capacities and Specificationschapter.
Mount wheel balance weights on the dome-side of the wheel only. Failure
to do so may result in loss of wheel weight or damage to brakes or
wheels.
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Oil-lubricated Front Wheel Bearings
During normal vehicle duty cycle, the lubricant and air inside the
hub/wheel cavity expands and, if not vented, causes pressure build-up
that could cause accelerated seal wear. You can use two venting methods
to prevent pressure build-up:
•A slit or small hole in the rubber check vent
•The window.
Over a period, 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 helps make sure that you can easily observe the
lubricant level through the window as intended. In situations where the
window is clean on the outside but discolored on the inside, you can
check the lubricant level by inserting a finger through the rubber check
vent hole.
The specified lubricant level for a window-type hubcap is from the
minimum line to five–sixteenth inch (8 millimeters) above the minimum
line. If the lubricant level should suddenly drop dramatically below the
minimum level, see theWorkshop Manualfor diagnostic procedure.
Installation, Tightening and Alignment
Make sure the threads on the studs and nuts are clean to permit correct
torque when installing wheels. 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 properly tightening the rim or wheel, check it for proper 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 points out the high spot. A high spot does not necessarily
indicate unevenly tightened lug nuts, but may be the result of a bent
wheel.
Use the following installation procedure:
1. Slide inner rear or front tire and wheel in position over studs and push
it back as far as possible. Use care so you do not damage the threads on
the studs.
250Wheels and Tires
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Observation Maintenance Operation
Insufficient power shown in loaded
practice stop.Inspect the automatic slack
adjuster function.
Subpar vehicle handling qualities. Check the operation of the brakes,
clutch and steering.
1,2
Excessive noise from under the
cab or engine compartment.Inspect your vehicle for missing,
damaged or mislocated noise
shields.
Excessive engine noise. Check the engine performance and
the engine governor.
Engine overheats; excessive fan
noise; fan constantly runs at high
speed or wobbles due to worn
bearings.Inspect the fan, fan shroud and fan
clutch.
Excessive exhaust noise; you smell
exhaust fumes.Inspect the entire exhaust system
for holes, leaks, breakage,
looseness and corrosive damage.
Excessive engine compartment
noise.Inspect the engine air induction
system (including air ducts and air
filter) for loose, damaged or
missing components.
Poor steering; wandering;
excessive tire wear.Check front end alignment, inspect
the tires and tire pressure.
3
Vibration or abnormal tire wear
indicating imbalance.Balance the wheels and the tires.
Hard shifting or excessive
vibration.Check the transmission and engine
mountings.
2
High effort to shift; noisy
transmission.Check and adjust transmission
controls.2
Insufficient full-throttle power;
backfiring.Check fuel pump pressure.
Radiator cap does not hold
pressure.Clean the cap seal and cap surface
on the radiator.
Electrical power supply has
diminished.Check the battery terminals for
corrosion.
344Scheduled Maintenance
2015 F-650/750(f67)
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