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Pinion Shaft
The input shaft in a driving axle that is usually a part of the smaller driving or input hypoid gear of a
ring and pinion gearset.
Pitch
The physical quality of sound that relates to its frequency. Pitch increases as frequency increases and
vice versa.
Pumping Feel
A slow, pulsing movement.
Radial/Lateral
Radial is in the plane of rotation; lateral is at 90 degrees to the plane of rotation.
Rattle
A random and momentary or short duration noise.
Ring Gear
The large, circular, driven gear in a ring and pinion gearset.
Road Test
The operation of the vehicle under conditions intended to produce the concern under investigation.
Roughness
A medium-
frequency vibration. A slightly higher frequency (20 to 50 Hz) than a shake. This type of
vibration is usually related to drivetrain components. Runout Item Description
1 Lateral runout
2 Radial runout Klj . 8 ba
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Lateral runout means measuring the movement or "wobble" of a wheel or tire at the sidewall. Radial
runout means measuring the out-of-
round at the tread surface.
Rustling
Intermittent sound of varying frequency (100- 2000 Hz), sounds similar to shuffling through leaves.
Shake
A low- frequency vibration (5-20 Hz), usually with visible component movement. Usually relates to tires,
wheels, brake drums or brake discs if it is vehicle speed sensitive, or engine if it is engine speed
sensitive. Also referred to as a shimmy or wobble.
Shimmy
An abnormal vibration or wobbling, felt as a side- to-side motion of the steering wheel in the driveshaft
rotation. Also described as waddle.
Shudder
A low- frequency vibration that is felt through the steering wheel or seat during light brake application.
Slap
A resonance from flat surfaces, such as safety belt webbing or door trim panels.
Slip Yoke/Slip Spline
The driveshaft coupling that allows length changes to occur while the suspension articulates and while
the driveshaft rotates.
Squeak
A high- pitched transient sound, similar to rubbing fingers against a clean window.
Squeal
A long- duration, high- pitched noise.
Static Balance
The equal distribution of weight around the wheel. Statically unbalanced wheel and tire assemblies can
cause a bouncing action called wheel tramp. This condition will eventually cause uneven tire wear.
Tap
A light, rhythmic, or intermittent hammering sound, similar to tapping a pencil on a table edge.
Thump
A dull beat caused by two items striking together. Tick Klj . 9 ba
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A rhythmic tap, similar to a clock noise.
Tip-
In Moan
A light moaning noise heard during light vehicle acceleration, usually between 40- 100 km/h (25-65
mph).
TIR
The acronym for total indicated runout is TIR.
Tire Deflection
The change in tire diameter in the area where the tire contacts the ground.
Tire Flat Spots
A condition commonly caused by letting the vehicle stand while the tires cool off. This condition can be
corrected by driving the vehicle until the tires are warm. Also, irregular tire wear patterns in the tire
tread resulting from wheel- locked skids.
Tire Force Vibration
A tire vibration caused by variations in the construction of the tire that is noticeable when the tire
rotates against the pavement. This condition can be present on perfectly round tires because of
variations in the inner tire construction. This condition can occur at wheel rotation frequency or twice
rotation frequency.
Transient
A noise or vibration that is momentary, a short duration.
Two- Plane Balance
Radial and lateral balance.
Vibration
Any motion, shaking or trembling, that can be felt or seen when an object moves back and forth or up
and down.
Whine
A constant, high- pitched noise. Also described as a screech.
Whistle
High- pitched noise (above 500 Hz) with a very narrow frequency band. Examples of whistle noises are
a turbocharger or airflow around an antenna.
Wind Noise
Any noise caused by air movement in, out or around the vehicle. Klj . 10 ba
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