Glossary of Terms Used In Pinpoint Tests
AccelerationAcceleration can be light, medium, or Wide Open Throttle (WOT).
Light
Increase speed at less than half throttle.
Medium
Increase speed at half to nearly full throttle.
WOT
Increase speed at wide open throttle.
Ambient Temperature
Surrounding or prevailing temperature.
Articulation
Vertical movement of the front or rear axle relative to the frame.
Belt Chirp
High pitched short duration noise usually caused by belt misalignment.
Belt Squeal
High pitched long duration noise usually caused by belt slippage.
Boom
A low frequency (sometimes cycling) noise.
Bound Up
Refers to an isolation mount or component that is stressed and therefore transmits vibration and/or noise instead of dampening or isolating it.
Brakes Applied
Use brakes to keep vehicle from moving with transmission in gear or in DRIVE.
Camber
The angle formed between the front wheel spindle axis and horizontal as 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 as measured looking from the side of the vehicle.
Chuckle
Refers to the noise that occurs on the coast driving phase; usually caused by excessive clearance due to differential gear wear or by a damaged tooth on the coast side of the final drive ring gear.
Clunk
Short, dull sound usually associated with the transmission engaging from reverse to drive.
Coast/Deceleration
The vehicle is in motion and the transmission is engaged, but no pressure is applied to the accelerator pedal. Speed control, if 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 made.
Coupling Shaft
The front shaft in a two-piece driveline system.
CPS
Cycles per second.
Cruise
Constant speed on level ground; neither accelerating nor decelerating.
Deceleration
Slowing of 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, In a four-wheel drive, it is the shaft between the transfer case and front axle.
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 engine, 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's mass center is not concentric to the rotation center.
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.
Gravelly Feel
A grinding or growl in a component; similar to the feel experienced when driving on gravel.
Harshness
A firmer than usual response of a component.
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, imbalance often causes vibration.
Inboard
Toward the vehicle centerline.
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.
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 used with bound-up condition.
NVH
Noise, vibration, and harshness.
Outboard
Away from the centerline of the vehicle.
Pinion Shaft
The input shaft to a driving axle is usually a part of the smaller driving or input hypoid gear of a ring and pinion gearset.
Pumping Feel
Slow pulsing movement.
Radial/Lateral
Radial is in the plane of rotation; lateral is at 90 degrees to the plane of rotation.
Ring Gear
The large, circular, driven gear in a ring and pinion gear set.
Road Test
Operation of the vehicle under conditions intended to produce the problem being investigated.
Runout
Rotational center is not concentric to the geometric center.
Shake
Low frequency vibration; usually with visible movement.
Slip Yoke/Slip Spline
The driveshaft coupling which allows length changes to occur while rotating between the transmission and driveshaft.
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 movement.
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 wheel-locked skids.
Two-Plane Balance
Radial and lateral balance.
Vibration
Abnormal, regular, movement that can be seen, felt, or heard.