Glossary of Terms Used In Pinpoint Tests

Acceleration Can Be:
Light
Increase speed at less than half-throttle.
Heavy
Increase speed at half- to nearly full throttle.
WOT
Increase speed at wide-open throttle.

Ambient Temperature
Temperature in the current location.

Articulation
Vertical movement of the front or rear axle relative to the frame.

Belt Chirp
High-pitched, short duration noise usually caused by
misalignment of the drive belt.

Belt Squeal
High-pitched, long duration noise usually caused by
drive belt slippage. This slippage can be caused by a
lack of the proper tension or by binding in one or more
pulleys.

Boom
Low-frequency noise, often felt as well as heard.

Bound Up
Refers to an isolation mount that is stressed and
therefore transmits vibration or noise instead of
dampening it.

Brakes Applied
Use brakes to keep vehicle from moving with
transmission in gear or DRIVE.

Camber
The angle of the front wheel spindle from the vertical,
measured looking from the front of the vehicle.
Camber is positive when the wheel tops are further
apart than the wheel bottoms.


Caster
The angle of the front wheel spindle from the vertical, measured looking from the side of the vehicle. Caster is positive when the top of the front wheel spindle is to the rear of the vehicle compared to the bottom of the spindle.

Chuckle
The sound of a stick hitting the spokes of a moving wheel. Usually found in the differential when the pinion gear is not meshing properly with the ring gear.

Clunk
Short, dull sound usually associated with the transmission engaging or when accelerating.

Coast/Deceleration
The vehicle is in motion and the transmission engaged, but no pressure is applied to the accelerator pedal and speed control, if so equipped, is disengaged.

Coast/Neutral Coast
The vehicle is in motion with the transmission disengaged.

Controlled Rear Suspension Height
The height that a designated vehicle element should be at when driveline angle measurements are to be made.

Coupling Shaft
The front shaft in a two-piece driveline.

CPS
Cycles per second.

Cruise
Constant speed on level ground.


Deceleration
Slowing the vehicle by releasing the accelerator pedal, but without using the brakes.

Driveline Angles
Differences of alignment between the transmission output shaft, the driveshaft, and the rear axle pinion centerline.

Driveshaft
The shaft that powers the rear axle input shaft (pinion shaft). In a two-piece driveline, it is the rearmost shaft.

Drivetrain
Includes all power-transmitting components from the engine to the wheels; includes the clutch or torque converter, the transmission, the driveline, and the drive axle.

Drivetrain Damper
A weight attached to the transmission, the transfer case, or the axle. It is tuned by weight and placement to absorb vibration.

Engine Imbalance
Condition in which an engine which has run smoothly starts vibrating.

Engine Misfire
Ignition in one or more cylinders does not occur or occurs at the wrong time.

Engine Runup Test
Operation of the engine through the normal rpm range with the vehicle standing still and the transmission disengaged. This test is used for vibration checks.

Float
A drive mode on the dividing line between cruise and
coast where the throttle setting matches the engine
speed with the road speed.

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.

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

Harshness
A firmer response than usual in a suspension area.

Hose Clamp
A screw-type circular clamp.

Hz
Hertz; a frequency of one cycle per second.

Imbalance
Out of balance, heavier on one side than the other. In a rotating component, often causes vibration.

Inboard
Towards the vehicle centerline.

In-Phase
The in-line relationship between the forward coupling
shaft yoke and the driveshaft centering socket yoke or
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. May be corrected by grinding.

Neutral Engine Runup Test
Operation of the engine through the normal rpm range with the vehicle standing still and the transmission disengaged. This is used for vibration checks.

Neutralize/Normalize
Relieve stress, usually for bound-up condition.

NVH
Noise, vibration and harshness.

Outboard
Away from the centerline of the vehicle.

Pinion Shaft
The drive axle input shaft.

Pumping Feel
Slow pulsing movement.

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

Ring Gear
The large, circular, driven gear in a ring and pinion gearset.

Road Test
Operation of the vehicle under conditions intended to produce the condition being investigated.

Runout
The amount out of round.

Shake
Low-frequency vibration usually with visible movement.

Slip Yoke/Slip Spline
The driveshaft coupling which allows length changes while rotating.

Tip-In Moan
A light moaning noise heard when the vehicle is lightly accelerated, usually between 40-100 kph (25-65 mph).

TIR
Total indicator runout.

Tire Deflection
The change in tire diameter where the tire contacts the ground.

Tire Force Vibration
Variations in the tire structure which result in vibration when rolling.

Tire Flat Spots
Wear caused by skidding.

Two-Plane Balance
Radial and lateral balance.

Vibration
Abnormal, regular, short duration movement that can be seen, felt, or heard.