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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.
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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 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).
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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.
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Note:Make sure the tire valve stem clears the brake caliper when
installing the tire and rim assembly on disc-brake equipped axles. The
use of a tire manufacturer’s stem forming tool is the only acceptable
method of obtaining clearance when necessary.
Proper Torque
It is important to tighten and maintain wheel and rim mounting nuts to
the proper torque. Loose nuts or over-tightened nuts can lead to
premature wear and possible failure of the wheel or mounting hardware.
Changing Wheel Types
WARNING:Use only the same type and style wheels and
mounting hardware to replace original parts. Failure to do so may
result in an assembly that looks fine, but does not fit together properly.
This could possibly cause wheel or fastener failures which could result
in property damage, personal injury or death.
Note:Do not attempt to mix stud-piloted wheels or fasteners with
hub-piloted wheels or fasteners.
Note:Do not change from aluminum wheels to steel wheels or
vice-versa without changing the mounting hardware required or, with
flange nut mounting systems, changing the hub and stud assembly.
Consult your dealer or wheel or rim distributor before attempting any
wheel or fastener changes.
TECHNICAL SPECIFICATIONS
Wheel Lug Nut Torque Specifications
Note:Do not use lubrication on dry threads. Where excessive corrosion
exists, a light coat of lubricant on the first three threads of the stud bolt
is permitted. Keep lubricant away from:
•Hex nut and rim clamp contact surfaces.
•Cap nut ball face and ball seat on the disc wheel.
•Flange nut washer surface and flat on the disc wheel.
Size Nut MountingTorque
ft-lb N•m
22 mm Flange 450–500 610–678
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TECHNICAL SPECIFICATIONS
Component Lubrication TypeViscosity / Ambient
Temperature / NotesEquivalent Ford
Part Name / Number
Non-driving front axle
Eaton-Spicer axle
(generic) - front axle
wheel bearing oilMultipurpose EP gear
lube of API GL-5
quality meeting
MIL-PRF-2105E
specifications including
synthetic lubricants.
Do not mix
conventional and
synthetic lubricants.SAE 75W:
–40°F to –15°F
(–40°C to –26°C)Motorcraft® SAE
75W-140 Synthetic
Rear Axle Lubricant /
XY–75W140–QL
SAE 75W-80:
–40°F to 80°F
(–40°C to 27°C)
SAE 75W-140:
–40°F and above
(–40°C and above)
SAE 80W-140:
–15°F and above
(–26°C and above)
SAE 85W-140:
10°F and above
(–12°C and above)
SAE 80W-90:
–15°F to 100°F
(–26°C to 38°C)Motorcraft® SAE
80W-90 Premium Rear
Axle Lubricant /
XY–80W90–QL
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Component Lubrication TypeViscosity / Ambient
Temperature / NotesEquivalent Ford
Part Name / Number
Spicer axle - front axle
wheel bearing oilMultipurpose EP gear
lube of API GL-5
quality meeting
MIL-PRF-2105E
specifications including
synthetic lubricants.
Do not mix
conventional and
synthetic lubricants.SAE 75W:
–40°F to 32°F
(–40°C to 0°C)Motorcraft® SAE
75W-140 Synthetic
Rear Axle Lubricant /
XY–75W140–QL
SAE 75W-140:
–40°F and above
(–40°C and above)
SAE 80W-140:
–15°F and above
(–26°C and above)
SAE 85W-140:
10°F and above
(–12°C and above)
SAE 140W:
40°F and above
(4°C and above)
SAE 80W:
–15°F to 70°F
(–26°C to 21°C)Motorcraft® SAE
80W-90 Premium Rear
Axle Lubricant /
XY–80W90–QL
SAE 90W:
10°F to 100°F
(–12°C to 38°C)
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Component Lubrication TypeViscosity / Ambient
Temperature / NotesEquivalent Ford
Part Name / Number
Eaton-Spicer axle,
Spicer axle - Front
axle wheel bearing
grease, tie rod ends,
drag link, kingpin and
bushingEP2 Lithium
complex-based moly
grease (or equivalent)
GC/LB NLGI #2
multi-purpose lithium
complex greaseNote:Eaton-Spicer
and Meritor Easy Steer
axles: With chassis
load on axle, force
grease through thrust
bearings; then with
axle lifted clear of the
floor, force grease
between kingpin and
bushing surfaces.Motorcraft® Premium
Long Life Grease /
XG-1-C
Steering
Power steering fluid MERCON® V ATF — MERCON® V /
XT-5-QMC; XT-5-QM;
XL-14
Steering gear Ross TAS
- Output Seal, Steering
column U-joints / slip
jointGC/LB NLGI #2 lithium
complex-based moly
grease or
multi-purpose lithium
complex grease— Motorcraft® Premium
Long Life Grease /
XG-1-C
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Component Lubrication TypeViscosity / Ambient
Temperature / NotesEquivalent Ford
Part Name / Number
Driveshaft
U-joint GC/LB NLGI #2 lithium
complex-based moly
grease or
multi-purpose lithium
complex grease— Motorcraft® Premium
Long Life Grease /
XG-1-C
Clutch
Release bearing /
shafts / forkGC/LB NLGI #2 lithium
complex-based moly
grease or
multi-purpose lithium
complex grease— Motorcraft® Premium
Long Life Grease /
XG-1-C
Reservoir DOT 3, WSS-M6C62-A
or WSS-M6C65-A1— High Performance DOT
3 Motor Vehicle Brake
Fluid, PM-1-C (U.S.) or
CPM-1-C (Canada)
Cooling System
Engine coolant WSS-M97B44-D2 — Motorcraft® Orange
Antifreeze/Coolant
Prediluted/
VC-3DIL-B (U.S.)
CVC-3DIL-B (Canada)
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