2003 FORD MUSTANG differential

DIAGNOSIS AND TESTING
Wheels And Tires
Inspection and Verification
WARNING: A vehicle equipped with a Traction- Lok® differential will always have both
wheels driving. If, while the vehicle is being serviced, only one wheel is raised off the ground
and the rear axle is driven by the engine, the wheel on the ground could drive the vehicle off
the stand or jack. Be sure both rear wheels are off the ground.
WARNING: Never run the engine with one wheel off the ground, for example, when
changing a tire. The wheel(s) resting on the ground could cause the vehicle to move.
WARNING: Do not balance the wheels and tires while they are mounted on the vehicle.
Possible tire disintegration or differential failure could result, causing personal injury and
extensive component damage. Use off- vehicle wheel and tire balancer only.
Be sure to follow the warnings when carrying out inspection and verification.
Road Test
Verify the customer concern by carrying out a road test on a smooth road. If any vibrations are
apparent, refer to Section 100 - 04 .
To maximize tire performance, inspect for signs of incorrect inflation and uneven wear, which may
indicate a need for balancing, rotation, or front suspension alignment.
Correct tire pressure and driving techniques have an important influence on tire life. Heavy cornering,
excessively rapid acceleration and unnecessary sharp braking increases tire wear.
Replacement tires must follow the recommended:
ztire sizes.
z speed rating.
z load range.
z tire construction type.
Use of any other tire size or type can seriously affect:
zride.
z handling.
z speedometer/odometer calibration.
z vehicle ground clearance.
z tire clearance between the body and chassis.
SECTION 204-
04: Wheels and Tires 2003 Mustang Workshop Manual Klj . 1 ba
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REMOVAL AND INSTALLATION
Wheel And Tire
Removal
1. CAUTION: Do not use heat to loosen a seized wheel nut (1012). Heat can damage
the wheel and wheel bearings.
NOTE: To avoid damage or scratching to the center cap, place facing up when removed.
Loosen the wheel nuts. 1. NOTE: To avoid wheel damage, do not twist wrench when removing center cap.
Remove the center cap, if equipped.
2. Loosen, but do not remove, the wheel nuts.
2. CAUTION: Never use the differential housing as a lifting point.
Raise the vehicle until the tire clears the ground. For additional information, refer to Section 100 - 02 .
3. CAUTION: Do not use heat to loosen a seized wheel because heat can shorten the
life of the wheel and damage the wheel bearings. If the wheel cannot be removed by
hand, use a wheel puller to remove the seized wheel.
Remove the wheel and tire assembly.
zRemove the wheel nuts.
z Remove the wheel and tire.
SECTION 204-
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Inspection and Verification
Certain axle noise or vibration symptoms are also common to the engine, transmission, wheel
bearings, tires, and other parts of the vehicle. For this reason, be sure that the cause of the trouble is
in the axle before disassembling, adjusting or repairing the axle. Refer to
Section 100 - 04 .
Certain driveshaft vibration symptoms are common to the front engine accessory drive (FEAD), the
engine, transmission or tires. Be sure the cause of the concern is the driveshaft before repairing or
installing a new driveshaft. Refer to Section 100 - 04 .
Certain symptoms may be caused by Traction- Lok® differentials (4026). Check the vehicle certification
label and axle identification tag to determine the type of differential. Refer to Section 100 - 01 .
Noise Acceptability
NOTE: A gear-driven unit will produce a certain amount of noise. Some noise is acceptable and
audible at certain speeds or under various driving conditions such as a newly paved blacktop road.
Slight noise is not detrimental to the operation of the axle and is considered normal.
With the Traction- Lok® differential axle, slight chatter noise on slow turns after extended highway
driving is considered acceptable and has no detrimental effect on the locking axle function.
Universal Joint (U- Joint) Inspection
Place the vehicle on a frame hoist and rotate the driveshaft (4602) by hand. Check for rough operation
or seized U- joints. Install a new U- joint if it shows signs of seizure, excessive wear, or incorrect
seating. Refer to Section 205 - 01 .
Analysis of Leakage
Clean up the leaking area enough to identify the exact source. An axle leak can be caused by the
following. zAxle lubricant level is too high.
z Worn or damaged axle shaft seals or differential seals.
z Differential housing is cracked.
z Flange yoke seat is worn or damaged.
z Pinion flange is scored or damaged.
z Axle cover is not sealed.
z Vent is plugged. Klj . 2 ba
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Repair the axle as necessary. Make sure the axle lubricant is at the correct level. Refer to
Specifications in this section.
Axle Vent
NOTE:
If a plugged vent cannot be cleared, install a new one.
A plugged vent will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs,
check the vent. Make sure the vent hose is not kinked. Remove the hose from the vent nipple and
clear the hose of any foreign material. While the hose is removed, pass a length of mechanics wire in
and out of the vent to clean it. Connect the hose when done.
Flange Yoke Seal
Leaks at the axle drive pinion seal originate for the following reasons:
zSeal was not correctly installed.
z Poor quality seal journal surface.
Any damage to the seal bore (dings, dents, gouges, or other imperfections) will distort the seal casing
and allow leakage past the outer edge of the axle drive pinion seal.
The axle drive pinion seal can be torn, cut, or gouged if it is not installed carefully. The spring that
holds the axle drive pinion seal against the pinion flange may be knocked out and allow leakage past
the lip.
The rubber lips can occasionally become hard (like plastic) with cracks at the oil lip contact point. The
contact point on the pinion flange may blacken, indicating excessive heat. Marks, nicks, gouges, or
rough surface texture on the seal journal of the pinion flange will also cause leaks.
When a seal leak occurs, install a new seal and check the vent and the vent hose to make sure they
are clean and free of foreign material.
Axle Shaft Seals
Axle shaft oil seals are susceptible to the same kinds of damage as axle drive pinion seals if incorrectly
installed. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. The
axle shaft journal surface must be free of nicks, gouges, and rough surface texture.
Differential Seals
Refer to Section 205 - 02A or
Section 205 - 02B .
Analysis of Vibration WARNING: A vehicle equipped with a Traction- Lok® differential will always have both
wheels driving. If only one wheel is raised off the floor and the rear axle is driven by the engine,
the wheel on the floor could drive the vehicle off the stand or jack. Be sure both rear wheels are
off the floor.
Few vibration conditions are caused by the rear axle. On a vibration concern, follow the diagnosis
procedure in Section 100 - 04 unless there is a good reason to suspect the axle.
Tires Klj . 3 ba
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WARNING: Do not balance the wheels and tires while they are mounted on the vehicle.
Possible tire disintegration/differential failure could result, causing personal injury/extensive
component damage. Use an off- vehicle wheel and tire balancer only.
Most vibration in the rear end is caused by tires or driveline angle.
Vibration is a concern with modern, high- mileage tires if they are not "true" both radially and laterally.
They are more susceptible to vibration around the limits of radial and lateral runout of the tire and
wheel assembly. They also require more accurate balancing. Wheel and tire runout checks, truing and
balancing are normally done before axle inspection. Refer to Section 204 - 04 .
Driveline Angle
Driveline angularity is the angular relationship between the engine crankshaft (6303), the driveshaft,
and the rear axle pinion. Factors determining driveline angularity include ride height, rear spring, and
engine mounts.
Driveline Angle
An incorrect driveline (pinion) angle can often be detected by the driving condition in which the
vibration occurs.
zA vibration during coastdown from 72 to 56 km/h (45 to 35 mph) is often caused by an
excessive U-joint angle at the axle (pinion nose downward).
z A vibration during acceleration, from 56 to 72 km/h (35 to 45 mph) may indicate an excessive U- joint angle at the axle (pinion nose upward). Item Description
1 Bottom of the frame
2 Engine crankshaft centerline
3 Engine angle
4 Driveshaft and coupling shaft centerline
5 Driveshaft and coupling shaft angle
6 Rear axle pinion centerline
7 Axle pinion angle Klj . 4 ba
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NOTE:
A low-pitched rumble normally associated with a worn/damaged wheel bearing can also be
caused by tires.
A wheel bearing noise can be mistaken for a pinion bearing noise. Check the wheel bearing for a
spalled cup, and spalled/damaged rollers. Check the wheel bearing for rotating smoothness and end
play. Install a new wheel bearing if any of these concerns are detected.
If the wheel bearing is damaged, the roller surface on the axle shaft may also be damaged. Install a
new axle shaft if any damage is detected.
Chuckle
Chuckle that occurs on the coast driving phase is usually caused by excessive clearance between the
differential gear hub and the differential case bore.
Damage to a gear tooth on the coast side can cause a noise identical to a chuckle. A very small tooth
nick or ridge on the edge of a tooth can cause the noise.
Clean the gear tooth nick or ridge with a small grinding wheel. If the damaged area is larger than 3.2
mm (1/8 inch), install a new gearset.
To check the ring gear and pinion, remove as much lubricant as possible from the gears with clean
solvent. Wipe the gears dry or blow them dry with compressed air. Look for scored or damaged teeth.
Also look for cracks or other damage.
If either gear is scored or damaged badly, install a new ring gear and pinion. Klj . 7 ba
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crayon or chalk.
6. While holding the crayon or chalk against the tire, rotate the wheel slowly in the opposite direction until the feeling of driving the rear axle is encountered again.
7. Measure the length of the crayon or chalk mark on the tire. zIf the length of the mark is 25.4 mm (1 inch) or less, the rear axle backlash is within
allowable limits.
z If the chalk mark is greater than 25.4 mm (1 inch), check for these conditions:
„Elongation of the differential pinion shaft and holes in the differential case (4204).
„ Missing differential pinion thrust washer (4230) or differential side gear thrust
washer (4228).
„ Galling of the differential pinion shaft (4211) and bore.
„ Excessive ring gear and pinion backlash. Follow the procedure for the type of rear
axle to check backlash.
Axle Shaft Bearing Noise
Axle bearing shaft noise is similar to gear noise and differential pinion bearing whine. Axle shaft
bearing noise will usually distinguish itself from gear noise by occurring in all driving modes (drive,
coast, and float), and will persist with the transmission in NEUTRAL while the vehicle is moving at the
speed in which the concern is occurring. If the vehicle makes this noise, remove the suspect axle
shaft, install a new bearing and a new axle seal. Re- evaluate the vehicle for noise before removing any
internal components.
Bearing Rumble
Bearing rumble sounds like marbles being tumbled. This condition is usually caused by a
worn/damaged wheel bearing. The lower pitch is because the wheel bearing turns at only about one-
third of the driveshaft speed. Wheel bearing noise also may be high- pitched, similar to gear noise, but
will be evident in all four driving modes.
Symptom Chart
Symptom Chart Condition
Possible Sources Action
z Traction- Lok®
does not work in
snow, mud or on
ice z
Differential. zCARRY OUT the Traction-
Lok® Differential Operation
Check in this section. REPAIR
as necessary. REFER to
Section 205 - 02A or
Section 205 - 02B .
z Lubricant leaking
from the pinion
seal, axle shaft oil
seals z
Vent.
z Damage in the
seal contact area
or damaged or
worn seal. z
CLEAN the axle housing vent.
z INSTALL a new seal if
damage is found.
z Differential side
gears/pinion
gears are scored z
Insufficient
lubrication. z
INSTALL new gears. REFER
to Section 205 - 02A or
Section 205 - 02B . FILL the axle to
specification.
z Incorrect or
contaminated z
INSTALL new gears. REFER
to Section 205 - 02A or
Section Klj . 10 ba
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If no improvement is noted, rotate the clamps in opposite directions, equal distances from the best
position determined in Step 8. Separate the clamp heads about 13 mm (1/2 inch) and recheck for
vibration at the road speed.
Repeat the process with increasing separation until the best combination is found or the vibration is
reduced to an acceptable level.
10. Install the wheels and road test (vibration noticeable on the hoist may not be evident during the road test). If the vibration is still not acceptable, install a new axle driveline vibration damper
first, if so equipped. If the vibration is still not acceptable, refer to Section 205 - 02A or
Section 205 - 02B for differential case and ring gear runout checks.
Driveshaft Vibrates 1. Road test the vehicle to determine the critical vibration points. Note the road speed, the engine RPM, and the shift lever positions at which the vibration occurs.
2. Stop the vehicle, place the transmission lever in neutral and run the engine through the critical speed ranges determined in Step 1.
3. If no vibration is felt, balance the driveshaft. Refer to Driveline Vibration in this section.
Traction- Lok® Differential Operation Check
A Traction-Lok® differential can be checked for correct operation without removing it from the rear axle
housing.
WARNING: A vehicle equipped with a Traction- Lok® differential will always have both
wheels driving. If only one wheel is raised off the floor and the rear axle is driven by the engine, the wheel on the floor could drive the vehicle off the stand or jack. Be sure both rear wheels are Klj . 14 ba
192003 Mustang Workshop Manual
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