2008 FORD F750 suspension

Before hook-up, make sure:
•The fifth wheel jaws are fully opened.
•The fifth wheel is fully tilted back to prevent body damage when the
tractor is backed under a trailer.
•The trailer wheels are blocked and the trailer spring brakes are
adjusted and applied. Never chase a trailer.
•The brake hoses and light cords are clear of the fifth wheel.
Hook-up
1. Back the tractor squarely under the trailer, engaging the fifth wheel
jaws on the kingpin. Always back-up slowly, making sure the trailer is
neither too high nor too low. Avoid backing under the trailer from an
angle.
2. Connect the service and emergency brake hoses and trailer light
connector. Refer toTractor-trailer connectionin theAir suspension
section of this chapter, adhering to the warning and using the three-point
stance while connecting and disconnecting the trailer.
3. Inspect the jaws of the fifth wheel to be sure they have fully closed on
the trailer kingpin and the trailer plate is resting securely on the fifth
wheel.
4. Be sure the coupler release lever is in the locked position.
5. Charge the trailer brake system. Set the trailer brakes, either with the
hand valve or tractor protection valve. Pull against the trailer for an
additional check of proper hook-up. Do not pull hard enough to damage
or strain the equipment.
6. Set the tractor parking brakes and fully raise the trailer landing gear.
Refer toBrakesin this chapter for proper operation of the parking brake
and trailer brakes.
7. Check the operation of all trailer lights and correct any lights that may
be faulty.
Un-hook
1. Try to keep the tractor and trailer in a straight line.
2. Apply the parking brakes.
3. Lower the trailer landing gear, making sure it is on solid, level ground.
The weight of the trailer is to be on the landing gear.
4. Block the trailer wheels.
2008 F-650/750(f67)
Supplement
USA(fus)
Driving
132

Fuse/Relay
LocationFuse Amp
RatingFuse Description
15 10A Interior lamp relay, GEM, Vanity mirrors
16 15A High beams, Indicator
17 — Not used
18 5A Headlamp switch interior lighting
19 15A Engine control
20 5A Starting system
21 10A DRL resistor
22 15A Air horn, Air suspension dump, Two-speed
axle, Driver-controlled locking differential
23 10A Flasher
24 15A ABS, Air dryer, Vacuum pump, Fuel heater
relay
25 10A Function selector switch
26 10A RH low beam headlamp
27 — Not used
28 10A LH low beam headlamp
29 10A Cluster warning lamps, Gauges, GEM,
Hydraulic ABS
30 15A Allison electronic transmission
31 — Not used
Relay 1 — Interior lamps
Relay 2 — Not used
Relay 3 — Horn
Relay 4 — One-touch down window
Relay 5 — Not used
Power distribution box
Always disconnect the battery before servicing high current
fuses.
2008 F-650/750(f67)
Supplement
USA(fus)
Roadside Emergencies
137

such as the fuel sender, cranking motor, alternator and feed-through
studs should be cleaned and re-coated with a lubricant sealing grease
such as Motorcraft Silicone Brake Caliper Grease and Dielectic
Compound XG-3, or equivalent. This should include the ground cable
connector for batteries, engine and cab as well as the jump starting stud.
Accessory feed connections
Vehicle electrical systems are complex and often include electronic
components such as engine and transmission controls, instrument panels,
ABS, etc. While most systems operate on battery voltage (12 volts),
some systems can be as high as 90 volts or as low as five volts. Refer to
the Electrical Circuit Diagram Manuals, available from your vehicle’s
manufacturer, to ensure that any additional body lights and accessories
are connected to circuits that are both appropriate and not overloaded.
No modification should be made to any vehicle control system without
first contacting your dealer.
SUSPENSION INSPECTION
Note:Do not adjust air suspension height to any setting other than the
specified setting. Altering the height setting will change the driveline
angle and may result in unwarrantable component damage, such as
transmission component damage.
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 times.
•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.
2008 F-650/750(f67)
Supplement
USA(fus)
Maintenance and Specifications
193

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.
FRAME AND TOW HOOKS
Your vehicles chassis is manufactured with frame rails of either HSLA
steel or heat-treated steel. Each must be handled in a specific manner to
ensure 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.
U-BOLT NUT TORQUE
U-bolt diameter (nominal)
(all spring suspensions)U-bolt diameter (nominal)
Ft. lb. N•m
IROS Air w/15,500 lb. axles and
less260–300 353–407
IROS Air w/greater than 15,500 lb.
axles370–400 502–542
Hendrickson 23,000 lb. axle 370–400 502–542
2008 F-650/750(f67)
Supplement
USA(fus)
Maintenance and Specifications
194

Air suspension U-bolt checks and re-torquing procedures
1. Inspect the threads of the U-bolt and nut for rust and debris. Clean
the threads if contaminated.
2. Using a torque wrench, determine if any nuts can be turned with a
force below the specified torque.
3. Using the lowest discovered torqued nut as a starting point, retighten
the nuts using the sequence listed underAir suspension U-bolt and
U-bolt nut installation.
Air suspension U-bolt and U-bolt nut installation
1. Inspect the threads of the U-bolt and nut for rust and debris. Clean
the threads if contaminated.
2. Install the U-bolts and nuts and torque the nuts to 15 ft. lb. (20 N•m),
using a diagonal pattern.
3. Re-torque the nuts to 100 ft. lb. (136 N•m), using a diagonal pattern.
4. Re-torque the nuts to 200 ft. lb. (271 N•m), using a diagonal pattern.
5. Re-torque the nuts to 400 ft. lb. (542 N•m), using a diagonal pattern.
(For vehicles equipped with 14ACC, 14 ADN and 14ADP axles, do not
use Step 6.)
6. Re-torque the nuts to 425 ft. lb (576 N•m), using a diagonal pattern.
(For vehicles equipped with 14ACC, 14 ADN and 14ADP axles.)
7. Use the same diagonal pattern with each U-bolt nut re-torque.
Spring U-bolt checks
Check U-bolt nuts and re-torque every 36,000 miles (58,000 km) after
initial 1,000 miles (1,600 km) re-torque. The U-bolt and nut threads and
seats should be cleaned and lubricated to ensure peak condition when
re-torqued.
DRIVESHAFT
At the regular lubrication interval, check the universal joints for any
evidence of wear or looseness. Should driveshaft vibrations occur, stop
the vehicle immediately to avoid possible hazardous consequences or
damage to other components.
REAR AXLE LUBRICANT
Refer to theScheduled Maintenance Guidechapter for rear axle
lubricant level checks and lubricant change intervals.
2008 F-650/750(f67)
Supplement
USA(fus)
Maintenance and Specifications
195

If rib tire is used on front axle and lug or off-road type on rear axle
positions:
1.Front (Steering) Axle:Replace tires at front wheels when tread is
worn to 4/32 inch (3 mm) or less.
2.Rear Axles:Tires must be removed when the tread is worn to
2/32 inch (2 mm) or less. Tires identified with the word “re-groovable”
molded on the sidewall can be re-grooved. A minimum of 3/32 inch
(2.5 mm) of under-tread must be left at the bottom of the grooves.
Wheel and tire balancing
Out-of-round or out-of-balance wheels or tires can cause vehicle
vibration, bounce and shimmy. Replace damaged or out-of-round wheels.
Out-of-round tires and wheel assemblies can be corrected by re-clocking
the tire relative to the wheel.
The tire and wheel assembly should then be dynamically balanced.
Wear
Radial tires can exhibit three types of normal wear patterns: 1) Even,
2) Erosion, 3) Chamfer.
Even wearis a sign that the tire is being properly used and maintained.
Erosion wearhas also been called rolling wear, channel or river wear.
Erosion wear is found more often at free rolling tires. This is an
indication that the tire is being used in a slow wearing operation. What
happens is that the belt plies are held very rigid and the tread is not
allowed to distort as it passes through the contact area. Wear will only
occur at the edge of the tread. No corrective action required. If erosion
gets to be 1/16 inch (2 mm) or more, the tire may be rotated to a drive
axle.
Chamfer or shoulder wear,with tires inflated properly, is a normal
tendency of most radial tire designs. If both inside and outside shoulders
are wearing evenly around the tire, no further action is required.
Over-inflation is not effective in correcting this effect.
Tires: 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 will adversely affect the
handling of your vehicle, which is dangerous.
2008 F-650/750(f67)
Supplement
USA(fus)
Maintenance and Specifications
207

Rotating tires from one wheel position to another is a way often used to
even out many types of irregular wear or to avoid it altogether. Some of
the more effective tire rotation programs are:
•Steer tires that have developed some type of irregular wear pattern
can be rotated to drive axles if rib tires are being used on all wheel
positions. Applying steer tires to a drive position will often clean them
and they can be moved 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 will wear away tread rubber
relatively quickly in the early life of a tire when it is most likely to
develop an unusual wear pattern.
•Drive axle tires may be placed on the other end of the same axle so
that direction of rotation is reversed. This is often helpful if a heel and
toe or alternate lug wear pattern has developed.
Irregular wear can be minimized 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
Refer to chain manufacturer’s recommendation for correct tire chain
usage, installation and removal.
2008 F-650/750(f67)
Supplement
USA(fus)
Maintenance and Specifications
208

FACTORY AUTHORIZED SYSTEMS CHECKS
In the event that your vehicle experiences a component related concern,
please contact your Ford dealership. The Ford Motor Company Trained
Technicians who work at Ford dealerships are specifically trained to
understand your vehicle.
A proper repair begins with a thorough system check. A Factory
Authorized Systems Check can ONLY be found at a Ford dealership. In
some circumstances, the technician may need to request your
authorization to perform additional operations to determine the final
diagnosis. The technician’s goal is to ensure that your vehicle is fixed
right the first time, at the best value to you.
The following list represents several of the Factory Authorized Systems
Checks available at a participating Ford dealers:
•Air Conditioning
•Check Engine Light
•All Wheel Drive and 4x4
•Automatic Transmission
•Engine Cooling and Cabin Heating
•Steering and Suspension
•Charge/Start/Battery
•Wheel Alignment
•Anti-Lock Brake System
EMISSIONS CONTROL SYSTEM
To ensure the emissions control systems operate effectively, you should
have the services listed in the maintenance schedule performed at the
specified time and mileage/km intervals. You should avoid running out of
fuel or turning off the ignition while the vehicle is in motion, especially
at high speeds.
Because of high engine compartment and exhaust system
temperatures resulting from emissions equipment, do not park,
idle or operate your vehicle in dry grass or other dry ground cover
where the possibility of ground fire exists.
Do not make unauthorized modifications to the engine or vehicle.
Modifications causing increased amounts of unburned fuel to reach the
exhaust system can significantly increase the temperature of the engine
compartment and/or the exhaust system.
2008 F-650/750(f67)
Supplement
USA(fus)
Scheduled Maintenance Guide
229