Section 00-04: Noise, Vibration and Harshness
1996 F-150, F-250, F-350, Bronco and F-Super Duty Workshop Manual





Ambient Temperature

Surrounding or prevailing temperature. Normally, the temperature in the service area or outdoors, depending on where testing is taking place.



Vertical movement of the front driving or rear axle relative to the frame of the vehicle to which they are attached.


Belt Chirp

An intermittent noise usually at idle caused by belt misalignment.


Belt Squeal

A continuous noise caused by a frozen accessory or insufficient tension.



A very low-frequency (sometimes cycling) noise often accompanied by sensation of pressure on the ear drums.


Bound Up

Refers to a stressed, rubber-mounted component that transmits any NVH which would normally be isolated by the mount. See Neutralize.


Brakes Applied

When vehicle is stationary, service brakes applied with enough force to hold vehicle against movement with transmission in gear or drive.



Angle formed between front wheel spindle axis and horizontal as viewed from in front of the vehicle.

Camber is positive when the wheel tops are farther apart than the wheel bottoms.



Angle formed between the upper and lower ball joint centerline axis or the spindle pin axis and a vertical axis as viewed from the side of the vehicle. Caster is considered positive when the ball joint centerline axis or the top of the spindle pin axis is behind the vertical axis.



Condition where whole rear end vibrates and is heard when the vehicle is moving.



Excessive clearance or wear between the pinion gear and ring gear sounding like a stick against the spokes of a spinning bicycle wheel.



Metallic noise heard when the transmission is placed in reverse or drive or when the throttle is applied or released.



Engine/transmission engaged, foot off accelerator pedal.


Coast/Neutral Coast

Engine/transmission taken out of gear with driveshaft (4602)/driveline by placing transmission selector in Neutral or by depressing clutch (manual transmission).


Controlled Rear Suspension Height

The height at which the components of a particular vehicle should be set when driveline angle measurements are made.


Coupling Shaft

The front shaft in a two-piece driveline.



Cycles per second.



Steady highway speed, neither accelerating nor decelerating; even pressure on accelerator pedal on level ground.



Slowing of vehicle by releasing foot from accelerator at cruise and allowing engine to slow vehicle without application of brakes.


Driveline Angles

Difference of alignment between the transmission output shaft, driveshaft and rear axle pinion centerline.



Shaft which powers the rear axle input shaft (pinion shaft). Also, the rearmost shaft in a two-piece shaft.



Includes all power transmitting components from the engine to the wheels, including clutch/torque converter, transmission, driveline and rear drive axle.


Drivetrain Damper

A tuned weight attached to back of transmission, transfer case, or axle to absorb vibration.


Engine Imbalance

Some component in the engine which is normally smoothly balanced now causing a perceptible vibration in the vehicle.


Engine Misfire

One or more cylinders in the engine fails to fire at the proper time.


Engine Run-Up Test

Operation of engine through normal rpm range with vehicle standing still and transmission in neutral. Used for engine and accessory vibration check.


Flexible Coupling

A flexible joint in the exhaust pipe located between the catalytic converter and muffler, designed to eliminate binding conditions in the exhaust system and eliminate exhaust NVH.



A cruising drive mode in which throttle setting matches engine speed to road speed between cruise and coast.


Gravelly Feel

A grinding or growl in a component, similar to the feel experienced while driving on gravel.



A harder than usual behavior of a component, like riding a vehicle with overinflated tires.


Hose Clamp

Screw-type hose clamp.



Hertz (cycles per second).



Out of balance; more weight on one side of a rotating component causing shake or vibration.



Toward the centerline of the vehicle. See Outboard.



The in-line relationship between the forward coupling shaft yoke and the driveshaft centering socket yoke of a two-piece driveline.



Separate from the influence of other components.



Caused by a gear tooth damaged on the drive side of the final drive ring gear which can be corrected by grinding the damaged area.


Neutral Engine Run-Up Test (NERU)

Operation of engine through normal rpm range with vehicle sitting still, transmission in neutral. Used for engine and accessory vibration check.


Neutralize (Normalize)

To adjust to unstressed position. Used to describe various mounts and exhaust system hangers. See Bound Up.



Noise, vibration, harshness.



Toward the outside of the vehicle rather than toward the centerline. See Inboard.


Pinion Shaft

The input shaft to a driving axle, usually a part of the smaller driving or input gear of a ring and pinion gearset.


Pumping Feel

A very slow vibration that results in a movement of vehicle components, similar to pumping the service brakes slightly.



Radial is in the plane of rotation, lateral is at 90 degrees to the plane of rotation.


Ring Gear

The large gear, driven by the pinion gear of a ring and pinion driving axle gearset.


Road Test

Operation of vehicle under conditions designed to recreate the problem condition.



Out of round or wobble.



Low frequency vibration, usually results in visual movement of components.


Slip-Yoke (Slip-Spline)

Driveshaft coupling device (half of a U-joint) which compensates for changes in shaft length due to articulation of axle; used at one end of driveshaft.


Tip-In Moan

A light moaning noise heard when the vehicle is lightly accelerated, usually between 40-104 km/h (25-65 mph).



Total indicated runout.


Tire Deflection

Bending of the body of the tire during rotation.


Tire Force Vibration

Tire vibration caused by variations in the construction of the tire, resulting in a vibration when the tire rotates against the pavement. This condition may be present on perfectly round tires because of variations in the inner construction.


Tires Flat Spots

Irregular tire wear patterns in the tire tread resulting from wheel-locked skids.


Two-Plane Balance

Radial and lateral balance.



Unwanted excitation from a component that results in a sound or feel of movement.