The differential can be locked or unlocked when the vehicle is moving at
a constant speed of under 25 mph (40 km/h) and while the wheels are
not slipping. The differential must not be locked when the vehicle is
traveling down steep grades and traction is minimal.
The differential lock and differential lock light automatically disengage at
speeds above 25 mph (40 km/h). The differential lock remains off until
either the vehicle is restarted or the differential lock switch is turned off
then back on.
Turn the engine off and raise all drive wheels of the locker differential
axle in order to prevent the vehicle from moving when servicing the
wheels, tires or brakes. Axles equipped with a NoSPIN Detroit Locker
differential deliver power to both wheels even when only one wheel is on
the ground.
WARNING:Failure to raise all drive wheels with this type of
differential could cause the vehicle to move unexpectedly,
resulting in property damage, personal injury or death.
Care should be taken to avoid sudden accelerations when both drive
wheels are on a slippery surface.
WARNING:Sudden accelerations on slippery surfaces could
cause the wheels to spin, the vehicle to turn sideways on a
crowned road surface or in a turn, possibly resulting in loss of vehicle
control and personal injury.
Fluid Temperature
Axle operating temperatures normally do not exceed 100°F (38°C).
If the operating temperature exceeds 230°F (110°C), the rate of axle
lubrication oxidation increases and shortens the life of the lubricant and
seals, requiring axle lubrication changes to become more frequent to
preserve the axle. Extreme Pressure (EP) lubricants should not be run
consistently above 230°F (110°C).
Axle Conversions
WARNING:When operating a loaded vehicle, the driver must
keep all adjustable axles on the ground at all times, supporting
their share of the vehicle’s load. Failure to do so can overload other
axles, tires, wheels, springs, steering components, brakes and frames,
resulting in early component failure, loss of vehicle control, possible
property damage and personal injury.
144Transmission
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Parking
WARNING:When parking your vehicle, do not leave the
transmission in gear; if the key is in the on position and the
vehicle rolls, the engine could start. Failure to follow these instructions
could result in an unattended vehicle moving, possibly causing personal
injury or property damage.
Always use the parking brake. When parking on a grade, block the
wheels and turn the front wheels to one side so that if the vehicle rolls,
the front tires act against the curb to stop the vehicle. The front wheels
are more effective at stopping a rolling vehicle than the rear wheels.
Cold Weather
Note:Idling in cold weather does not heat the engine to its normal
operating temperature. Long periods of idling in cold weather can cause
a build-up of heavy deposits of carbon and rust on valve stems causing
them to stick which, in turn, can cause valvetrain damage.
Note:The use of winter fronts, or other air-restrictive devices mounted
in front of the radiator on vehicles with chassis-mounted charge air
coolers, are not recommended unless extremely cold weather conditions
exist. Airflow restriction can cause high exhaust temperatures, power
loss, excessive fan usage and a reduction in fuel economy. If you must
use a winter front, the device should have a permanent opening of at
least 120 square inches (774 square centimeters) directly in line with the
fan hub.
For best engine operation in temperatures of 32°F (0°C) or lower:
•Make sure the batteries are the correct type and are fully charged.
Check other electrical components to make sure they are in optimum
condition.
•Use a permanent-type engine coolant to protect the engine against
damage from freezing.
•If your vehicle is equipped with a water-fuel separator, drain it daily.
Fill the fuel tank at the end of daily operation to prevent
condensation in the fuel system.
•Use the proper engine oil and maintain it at its proper level.
•At temperatures of –4°F (–20°C) or below, it is recommended that
you use a crankcase-mounted coolant heater to improve cold engine
starting.
•If operating in arctic temperatures of –20°F (–29°C) or lower, consult
your truck dealer for information about special cold weather
equipment and precautions.
Driving Aids169
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Hot Weather
•Use a permanent-type engine coolant to protect the engine against
damage from overheating.
•Fill the fuel tank at the end of daily operation to prevent
condensation in the fuel system.
•Keep external surfaces of the engine, radiator, charge air cooler, A/C
condenser and accessories clean to avoid dirt build-up.
•Above normal coolant temperatures could be experienced while
driving in a transmission gear ratio which lugs the engine. To correct
this problem, engine speed should be increased by downshifting into
the next lower gear.
STEERING
Your vehicle is equipped with power steering. Power steering uses energy
from the engine to decrease the driver’s effort in steering the vehicle.
To help prevent damage to the power steering pump:
•Never hold the steering wheel to the extreme right or the extreme
left for more than a few seconds when the engine is running.
•Do not operate the vehicle with the power steering pump fluid level
below the ADD mark on the MAX. COLD side of the power steering
reservoir dipstick.
•Some noise is normal during operation. If the noise is excessive,
check for low power steering pump fluid level before seeking service
by your authorized dealer.
•Heavy or uneven steering efforts may be caused by low power
steering pump fluid level. Check for low power steering pump fluid
level before seeking service by your authorized dealer.
•Do not fill the power steering pump reservoir above the FULL mark
on the MAX. HOT side of the power steering reservoir dipstick, as
this may result in leaks from the reservoir.
If the power steering system breaks down (or if the engine is turned
off), you can steer the vehicle manually, but it takes more effort.
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.
170Driving Aids
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
*Specific GCWR and maximum trailer weight applicable to a given
F–650/750 model is dependent on many variables including transmission
capability. Check with your sales consultant for the exact rating on your
vehicle.
ESSENTIAL TOWING CHECKS
Service your vehicle more frequently if you tow a trailer. See your
scheduled maintenance information.
For load specification terms found on the Tire Label and Safety
Compliance Certification Label and for instructions on calculating your
vehicle’s load, seeLoad limitin theLoad Carryingchapter.
Hitches
Do not use a hitch that either clamps onto the bumper or attaches to the
axle.
Distribute the trailer load so 10-15% of the total trailer weight is on the
tongue.
Safety Chains
Note:Do not attach safety chains to the bumper.
Always connect the trailer’s safety chains to the frame or hook retainers
of your vehicle hitch.
To connect the trailer’s safety chains, cross the chains under the trailer
tongue and allow enough slack for turning tight corners. Do not allow the
chains to drag on the ground.
Trailer Brakes
WARNING:Do not connect a trailer’s hydraulic brake system
directly to your vehicle’s brake system. Your vehicle may not have
enough braking power and your chances of having a crash greatly
increase.
Electric brakes and manual, automatic or surge-type trailer brakes are
safe if installed properly and adjusted to the manufacturer’s
specifications. The trailer brakes must meet local and federal regulations.
The braking system of the tow vehicle is rated for operation at
the GVWR not GCWR.
176Towing
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
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 dirt, lint, etc.
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
and should only be performed by a qualified technician. 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. This should also be done
during other scheduled maintenance (tire rotation or service, wheel
bearing service, alignment, etc.). See the workshop manual for proper
procedures.
Toe-in
It is essential that correct toe-in and tire pressure be maintained 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, 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 equals
1 2steer axle loading).
206Maintenance
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Special applications may warrant a setting based on 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 does not drastically improve tire tread life.
Rear Axle
Regular inspections should include:
•checking for proper tightness of axle mounting U-bolt nuts, attaching
or mounting bolts and nuts. SeeSpring U-bolt checkslater in this
chapter.
•checking the axle for damage, binding, worn parts and adequate
lubrication.
NoSpin Detroit Locker Positive Locking Differential
Vehicles equipped with this type differential have the operator’s manual
supplied with the vehicle. See that manual for maintenance inspections.
Maintenance207
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
WARNING(Continued)
•Do not change from aluminum wheels to steel wheels or vice-versa
without changing the mounting hardware where required or, in some
cases with flange nut mounting systems, changing the hub and stud
assembly. Mixing components could cause wheel or fastener failures
and result in property damage, personal injury, or death.
WARNING:An inflated tire and rim can be very dangerous if
improperly used, serviced or maintained. To avoid serious injury,
never attempt to re-inflate a tire which has been run flat or seriously
under-inflated without first removing the tire from the wheel assembly
for inspection. Do not attempt to add air to tires or replace tires or
wheels without first taking precautions to protect persons and property.
All tires with Steel Carcass Plies (if equipped):This type of tire
utilizes steel cords in the sidewalls. As such, they cannot be treated like
normal light truck tires. Tire service, including adjusting the air pressure,
must be performed by personnel trained, supervised and equipped
according to Federal Occupational Safety and Health Administration
(OSHA) regulations. For example, during any procedure involving tire
inflation, the technician or individual must utilize a remote inflation
device, and make sure that all persons are clear of the trajectory area.
Wheels and Tires253
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)
Stay out of the trajectory (1) as indicated in the illustration.
WARNING:Do not mount tube type tires on tubeless wheels or
tubeless tires on tube type wheels. To do so could result in tire
or wheel failure and cause property damage, personal injury or death.
Preserving proper inflation pressure is a very important maintenance
practice to make sure safe vehicle operation and long life for the tires.
Failure to maintain correct inflation pressure may result in sudden tire
destruction, improper vehicle handling, and may cause rapid and
irregular tire wear. Therefore, inflation pressures should be checked daily
and always before long distance trips.
Follow the tire manufacturer’s recommended cold inflation pressure for
the tire size, type, load range (ply rating) and axle loading typical for
your operation. (Each steer axle tire load equals
1 2steer axle loading;
each drive tire load is1 4the axle loading if fitted with four tires).
254Wheels and Tires
2013 F-650/750(f67)
Owners Guide gf, 2nd Printing, March 2013
USA(fus)