Glossary of Terms Used In Pinpoint Tests
AccelerationAcceleration can be light, medium, or Wide Open Throttle (WOT).
Light
Less than half throttle.
Heavy
Half to nearly full throttle.
WOT
Wide open throttle.
Ambient Temperature
Surrounding or prevailing temperature, usually in the service area or outdoors.
Articulation
Vertical movement of the driving front wheel driveshaft and joint relative to the frame of the vehicle.
Belt Chirp
An intermittent noise at idle caused by belt misalignment.
Belt Squeal
High pitched long duration noise usually caused by a frozen accessory or insufficient tension.
Boom
A cycling, rhythmic noise often accompanied by a sensation of pressure on the eardrums.
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.
Camber
Camber is the amount that the centerline of the wheel is tilted inward or outward from the true vertical. If the top of the wheel is tilted outward, away from the vehicle, the camber is positive. If the top of the wheel is tilted inward, toward the vehicle, the camber is negative.
Caster
Caster is the forward or rearward tilt of the strut/ball joint centerline axis (the kingpin axis) with respect to the vertical. Caster is considered positive when the top of the kingpin axis is behind the vertical axis.
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 often heard when the transaxle engages or when accelerating.
Coast/Deceleration
Slowing the vehicle by releasing foot from the accelerator pedal and shaft at cruise and allowing the engine to slow the vehicle without application of the brakes.
Coast/Neutral Coast
Engine/transaxle taken out of gear by placing the gearshift lever in NEUTRAL (N) or by depressing the clutch pedal.
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.
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 middle of the RH front wheel driveshaft and joint to "soak up" or damp unwanted powertrain vibrations.
Engine Imbalance
Condition in which an engine which has run smoothly starts vibrating.
Engine Shake
Condition in which an engine's mass center is not concentric to the rotation center.
Engine Misfire
One or more cylinders in the engine fail to fire at the proper time.
Engine Runup Test
Operation of the engine through the normal rpm range with the vehicle standing still and the transaxle disengaged. This 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 response than usual, typically in the suspension system.
Hose Clamp
A screw-type circular clamp used to secure various hoses and tubes.
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.
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. Can 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 of possible bound-up components.
NVH
Noise, Vibration, and Harshness.
Outboard
Away from the centerline of the vehicle.
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, 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
Out of round or wobble.
Shake
Low frequency vibration; usually with visible movement.
Slip Yoke/Slip Spline
The driveshaft coupling which allows length changes to occur while suspension articulates and/or while driveshaft rotates.
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 in the area where the tire contacts the ground.
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 tire construction.
Tire Flat Spots
Commonly caused by letting the vehicle stand while the tires cool off. Can be cured by operating the vehicle again until the tires are warm. Also, irregular tire wear patterns in the tire tread resulting from wheel-locked skids or defective tires.
Two-Plane Balance
Radial and lateral balance.
Vibration
Abnormal, regular, or short duration movement that can be seen, felt, or heard.