4. While the noise is occurring, either place an EngineEAR probe near the IAC valve and the inlet
tube, or create a 6.35 mm (0.25 in)- 12.7 mm (0.50 in) air gap between the inlet tube and the
clean air tube. If the IAC valve is making the noise, install a new IAC valve.
5. Test the vehicle for normal operation.
Steering Gear Grunt/Shudder Test
1. Start and run the vehicle to operating temperature.
2. Set engine idle speed to 1200 rpm.
3. CAUTION: Do not hold the steering wheel against the stops for more than three to
five seconds at a time. Damage to the power steering pump will occur.
Rotate the steering wheel to the RH stop, then turn the steering wheel 90° back from that
position. Turn the steering wheel slowly in a 15° to 30° arc.
4. Turn the steering wheel another 90°. Turn the steering wheel slowly in a 15° to 30° arc.
5. Repeat the test with power steering fluid at different temperatures.
6. If a light grunt is heard or a low (50- 200 Hz) shudder is present, this is a normal steering system
condition.
7. If a loud grunt is heard, or a strong shudder is felt, fill and purge the power steering system.
Checking Tooth Contact Pattern and Condition of the Ring and Pinion
There are two basic types of conditions that will produce ring and pinion noise. The first type is a howl
or chuckle produced by broken, cracked, chipped, scored or forcibly damaged gear teeth and is
usually quite audible over the entire speed range. The second type of ring and pinion noise pertains to
the mesh pattern of the gear pattern. This gear noise can be recognized as it produces a cycling pitch
or whine. Ring and pinion noise tends to peak in a narrow speed range or ranges, and will tend to
remain constant in pitch.
1. Raise and support the vehicle. For additional information, refer to Section 100 - 02 .
2. Drain the axle lubricant. Refer to Section 205 - 02A for Ford 7.5 rear axles or
Section 205 - 02B for
Ford 8.8 integral axles.
3. Remove the carrier assembly or the axle housing cover depending on the axle type. Refer to Section 205 - 02A for Ford 7.5 rear axles or
Section 205 - 02B for Ford 8.8 integral axles.
4. Inspect the gear set for scoring or damage. Klj . 64 ba
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Wheel and tire NVH concerns are directly related to vehicle speed and are not generally affected by
acceleration, coasting or decelerating. Also, out-of-
balance wheel and tires can vibrate at more than
one speed. A vibration that is affected by the engine rpm, or is eliminated by placing the transmission
in NEUTRAL is not related to the tire and wheel. As a general rule, tire and wheel vibrations felt in the
steering wheel are related to the front tire and wheel assemblies. Vibrations felt in the seat or floor are
related to the rear tire and wheel assemblies. This can initially isolate a concern to the front or rear.
Careful attention must be paid to the tire and wheels. There are several symptoms that can be caused
by damaged or worn tire and wheels. Carry out a careful visual inspection of the tires and wheel
assemblies. Spin the tires slowly and watch for signs of lateral or radial runout. Refer to the tire wear
chart to determine the tire wear conditions and actions. Klj . 68 ba
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DESCRIPTION AND OPERATION
Wheel Alignment Angles
Camber and toe are adjustable on the front suspension systems. Front camber is adjusted by moving
the top of the strut and spring assembly. Rear camber is adjusted by means of eccentric cams on the
rear upper arms. Caster is preset at the factory and should only be adjusted after all other possible
sources have been inspected and corrected as necessary. Front toe is adjusted by the use of the front
wheel spindle tie rod (3280).
Camber
Negative and Positive Camber
Camber is the vertical tilt of the wheel (1007) when viewed from the front. Camber can be positive or
negative and has a direct effect on tire wear.
Caster
Caster is the deviation from vertical of an imaginary line drawn through the ball joints when viewed
from the side. Caster specifications in this section will give the vehicle the best directional stability
characteristics when loaded and driven. Caster setting is not related to tire wear.
SECTION 204-
00: Suspension System — General Information 2003 Mustang Workshop Manual Item Part Number Description
1 — Positive caster
2 — True vertical
3 — Steering axis Klj . 1 ba
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Wheel Track
Dogtracking
Dogtracking or thrust angle is the condition in which the rear axle is not square to the chassis. Heavily
crowned roads can give the illusion of dogtracking.
Wander
Wander is the tendency of the vehicle to require frequent, random left and right steering wheel (3600)
corrections to maintain a straight path down a level road. Item Description
1 Body reinforcement
2 Ride height (shortest distance)
3 Rear axle
Item Part Number Description
1 — Front track
2 — Rear track
Item Part Number Description
1 — Vehicle centerline
2 — Axle centerline
3 — Thrust angle Klj . 4 ba
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Shimmy
Shimmy, as observed by the driver, is large, consistent, rotational oscillations of the steering wheel
resulting from large, side-
to-side (lateral) tire/wheel movements.
Shimmy is usually experienced near 64 km/h (40 mph), and can begin or be amplified when the tire
contacts pot holes or irregularities in the road surface.
Nibble
Sometimes confused with shimmy, nibble is a condition resulting from tire interaction with various road
surfaces and observed by the driver as small rotational oscillations of the steering wheel.
Poor Returnability/Sticky Steering
Poor returnability and sticky steering is used to describe the poor return of the steering wheel to center
after a turn or steering correction is completed.
Drift/Pull
Pull is a tugging sensation, felt in the steering wheel, that must be overcome to keep the vehicle going
straight.
Drift describes what a vehicle with this condition does with hands off the steering wheel.
zDrift/pull may be induced by conditions external to the vehicle (i.e., wind, road camber).
Poor Groove Feel
Poor groove feel is characterized by little or no buildup of turning effort felt in the steering wheel as the
wheel is rocked slowly left and right within very small turns around center or straight- ahead (under 20
degrees of steering wheel turn). Efforts may be said to be "flat on center."
zUnder 20 degrees of turn, most of the turning effort that builds up comes from the mesh of gear
teeth in the steering gear (3504). In this range, the steering wheel is not yet turned enough to
feel the effort from the self- aligning forces at the road wheel or tire patch.
z In the diagnosis of a handling problem, it is important to understand the difference between
wander and poor groove feel. Klj . 5 ba
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