Glossary of Terms Used In Pinpoint Tests

Acceleration
- Light: Increase in speed at less than half throttle.
- Heavy: Half to full throttle increase in speed.
- WOT: Wide-open throttle.

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

Articulation
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.

Boom
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.

Camber
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.

Caster
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.

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

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

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

Coast/Deceleration
Engine/transmission engaged, foot off accelerator pedal.

Coast/Neutral Coast
Engine/transmission taken out of gear with driveshaft/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.

CPS
Cycles per second.

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

Deceleration
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.

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

Drivetrain
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.

Float
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.

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

Hose Clamp
Screw-type hose clamp.

Hz
Hertz (cycles per second).

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

Inboard
Toward the centerline of the vehicle. See Outboard. In-Phase The in-line relationship between the forward coupling shaft yoke and the driveshaft centering socket yoke of a two-piece driveline.

Isolate
Separate from the influence of other components.

Knock
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.

NVH
Noise, vibration, harshness.

Outboard
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/Lateral
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.

Runout
Out of round or wobble.

Shake
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 40-104km/h (25-65 mph).

TIR
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.

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