Ford Falcon. Manual — part 8

100-04-4

Noise, Vibration and Harshness

100-04-4

DESCRIPTION AND OPERATION (Continued)

applied and the transmission engaged. This test is

from side-to-side (wobble). Dynamically unbalanced

used for noise and vibration checks.

wheel and tyre assemblies can cause wheel shimmy.

Driveline Angles

Engine Imbalance

The differences of alignment between the

A condition in which an engine’s center mass is not

transmission output shaft, the driveshaft, and the rear concentric to the rotation center, causing excessive

axle pinion centerline.

motion.

Engine Misfire
When combustion in one or more cylinders does not

occur or occurs at the wrong time.

Engine Shake
An exaggerated engine movement or vibration that

directly increases in frequency as the engine speed

increases. It is caused by non-equal distribution of

mass in the rotating or reciprocating components.

Flexible Coupling
A flexible joint.

Float
A drive mode on the dividing line between cruise and

Item

Description

coast where the throttle setting matches the engine

speed with the road speed.

1

Engine

2

Driveshaft

Flutter

3

Differential

Mid to high (100-200 Hz) intermittent sound due to air

flow. Similar to a flag flapping in the wind.

Driveshaft

Frequency

The shaft that transmits power to the rear axle input

The rate at which a cycle occurs within a given time.

shaft (pinion shaft). In a two-piece driveshaft, it is the

rearmost shaft.

Gravelly Feel

Drivetrain

A grinding or growl in a component, similar to the feel

experienced when driving on gravel.

All power transmitting components from the engine to

the wheels; includes the clutch or torque converter,

Grind

the transmission, the transfer case, the driveshaft,

and the front or rear drive axle.

An abrasive sound, similar to using a grinding wheel,

or rubbing sand paper against wood.

Drivetrain Damper

Hiss

A weight attached to the engine, the transmission, the

transfer case, or the axle. It is tuned by weight and

Steady high frequency (200–800 Hz) noise. Vacuum

placement to absorb vibration.

leak sound.

Drone

Hoot

A low frequency (100-200 Hz) steady sound, like a

A steady low frequency tone (50-500 Hz), sounds like

freezer compressor. Also described as a moan.

blowing over a long neck bottle.

Drumming

Howl

A cycling, low-frequency (20–100 Hz), rhythmic noise

A mid-range frequency (200-800 Hz) noise between

often accompanied by a sensation of pressure on the

drumming and whine. Also described as a hum.

ear drums. Also described as a low rumble, boom, or

Hum

rolling thunder.

Mid-frequency (200-800 Hz) steady sound, like a

Dynamic Balance

small fan motor. Also described as a howl.

The equal distribution of weight on each side of the

Hz

centerline, so that when the wheel and tyre assembly

spins, there is no tendency for the assembly to move

Hertz; a frequency measured in cycles per second.

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100-04-5

Noise, Vibration and Harshness

100-04-5

DESCRIPTION AND OPERATION (Continued)

Imbalance
Out of balance; heavier on one side than the other. In

a rotating component, imbalance often causes

vibration.

Inboard
Toward the centerline of the vehicle.

Intensity
The physical quality of sound that relates to the

strength of the vibration (measured in decibels). The

higher the sound’s amplitude, the higher the intensity

and vice versa.

Isolate

Item

Description

To separate the influence of one component to

another.

1

Lateral runout

2

Radial runout

Knock
A heavy, loud, repetitious sound, like a knock on the

Rattle

door.

A random and momentary or short duration noise.

Moan

Rotary Blade Coupling (RBC)

A constant, low-frequency (100–200 Hz) tone. Also

described as a hum.

This part is attached to the rear axle on 4WD

vehicles. It includes an internal hydraulic pump and

Neutral Engine Run-Up (NERU) Test

clutch pack to control the torque supplied to the rear

axle/wheels. It also has an internal electromagnetic

The operation of the engine through the normal rpm

clutch to lock to the RCB for the 4WD ON mode. This

range with the vehicle standing still and the

unit is not to be disassembled and if necessary a new

transmission disengaged. This test is used to identify

unit must be installed.

engine related vibrations.

Ring Gear

Neutralize/Normalize

The large, circular, driven gear in a ring and pinion

To return to an unstressed position. Used to describe

gearset.

mounts. Refer to Bound Up.

Road Test

Outboard

The operation of the vehicle under conditions

Away from the centerline of the vehicle.

intended to produce the concern under investigation.

Ping

Roughness

A short duration, high-frequency sound, which has a

A medium-frequency vibration. A slightly higher

slight echo.

frequency (20 to 50 Hz) than a shake. This type of

Pinion Shaft

vibration is usually related to drivetrain components.

The input shaft in a driving axle that is usually a part

Runout

of the smaller driving or input hypoid gear of a ring

Lateral runout means measuring the movement or

and pinion gearset.

“wobble” of a wheel or tyre at the sidewall. Radial

Pitch

runout means measuring the out-of-round of the tyre

tread surface.

The physical quality of sound that relates to its

frequency. Pitch increases as frequency increases

Rustling

and vice versa.

Intermittent sound of varying frequency (100-200 Hz),

Pumping Feel

sounds similar to shuffling through leaves.

A slow, pulsing movement.

Shake

Radial/Lateral

A low-frequency vibration (5–20 Hz), usually with

visible component movement. Usually relates to tyres,

Radial is in the plane of rotation; lateral is at 90

wheels, brake drums or brake discs if it is vehicle

degrees to the plane of rotation.

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100-04-6

Noise, Vibration and Harshness

100-04-6

DESCRIPTION AND OPERATION (Continued)

speed sensitive, or engine if it is engine speed

warm. Also, irregular tyre wear patterns in the tyre

sensitive. Also referred to as a shimmy or wobble.

tread resulting from wheel-locked skids.

Shimmy

Tyre Force Vibration

An abnormal vibration or wobbling, felt as a

A tyre vibration caused by variations in the

side-to-side motion of the steering wheel in the

construction of the tyre that is noticeable when the

driveshaft rotation. Also described as waddle.

tyre rotates against the pavement. This condition can

be present on perfectly round tyres because of

Shudder

variations in the inner tyre construction. This condition

can occur at wheel rotation frequency or twice rotation

A low-frequency vibration that is felt through the

frequency.

steering wheel or seat during light brake application.

Transient

Slap

A noise or vibration that is momentary, a short

A resonance from flat surfaces, such as safety belt

duration.

webbing or door trim panels.

Two-Plane Balance

Slip Yoke/Slip Spline

Radial and lateral balance.

The driveshaft coupling that allows length changes to

occur while the suspension articulates and while the

Vibration

driveshaft rotates.

Any motion, shaking or trembling, that can be felt or

Squeak

seen when an object moves back and forth or up and

down.

A high-pitched transient sound, similar to rubbing

fingers against a clean window.

Whine

Squeal

A constant, high-pitched noise. Also described as a

screech.

A long-duration, high-pitched noise.

Whistle

Static Balance

High-pitched noise (above 500 Hz) with a very narrow

The equal distribution of weight around the wheel.

frequency band. Examples of whistle noises are a

Statically unbalanced wheel and tyre assemblies can

turbocharger or airflow around an antenna.

cause a bouncing action called wheel tramp. This

condition will eventually cause uneven tyre wear.

Wind Noise

Tap

Any noise caused by air movement in, out or around

the vehicle.

A light, rhythmic, or intermittent hammering sound,

similar to tapping a pencil on a table edge.

WOT

Thump

The acronym wide-open throttle is WOT.

A dull beat caused by two items striking together.

Tick
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 the total indicated runout is TIR.

Tyre Deflection
The change in tyre diameter in the area where the

tyre contacts the ground.

Tyre Flat Spots
A condition commonly caused by letting the vehicle

stand while the tyres cool off. This condition can be

corrected by driving the vehicle until the tyres are

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100-04-7

Noise, Vibration and Harshness

100-04-7

DIAGNOSIS AND TESTING

Noise, Vibration and Harshness (NVH)

To assist the service advisor and the technician, a

Write-up Job Aid and an NVH Diagnostic Guide are

included with this material. The Write-up Job Aid

serves as a place to record all important symptom

information. NHV Diagnostic Guide serves as a place

to record information reported on the Write-up Job Aid

as well as data from the testing to be carried out.
To begin a successful diagnosis, fill out the NVH

Diagnostic Guide, record the reported findings, then

proceed to each of the numbered process steps to

complete the diagnosis.

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