Definitions and Abbreviations

Definitions and Abbreviations
Throttle Position Definitions

Heavy Throttle
Approximately 75% of accelerator pedal travel.

Light Throttle
Approximately 25% of accelerator pedal travel.

Medium Throttle
Approximately 50% of accelerator pedal travel.

Wide-Open Throttle (WOT)
Full travel of the accelerator pedal (100% throttle).

Closed Throttle
Foot is off the accelerator pedal or pedal is not depressed (0% throttle).

Throttle-Related Shift Condition Definitions

Closed Throttle Manual Downshift
A condition where the engine is used to slow the vehicle by manually downshifting during a closed throttle coastdown.

Closed Throttle Coastdown
A full release of the accelerator pedal while the transmission remains in drive range, allowing the transmission to downshift as vehicle speed reduces.

WOT Detent Downshift
Quick apply of the accelerator pedal to its full travel, forcing a downshift.

WOT Upshifts/Downshifts
Accelerator pedal is fully depressed and transmission shifts sequentially through ranges as dictated by load and grade.

Shift Condition Definitions

Bump
A sudden and forceful apply of a clutch.

Delayed
A shift was expected but did not occur for several seconds, as during a manual downshift or WOT detent downshift. May also be defined as Late or Extended.

Double Bump
Two bumps felt during a clutch apply.

Early
Shift occurs at lower speed than expected, often accompanied by engine laboring after an upshift.

End Bump
A firmer feel at the end of a shift than at the start of a shift.

Firm
A noticeably quick apply of a clutch at medium or heavy throttle conditions. DO NOT confuse with Harsh or Rough.

Flare
A quick increase in engine speed along with a momentary loss of torque during a shift transition. This condition may also be defined as Slipping.

Harsh (Rough)
More noticeable clutch apply than Firm. Considered unacceptable at any throttle position.

Hunting
A repeating quick series of upshifts and downshifts that causes a noticeable change in engine speed (such as 4-3-4, etc.). Sometimes defined as Cycling.

Initial Feel
A distinctly firmer feel at the start of a shift than at the finish of a shift.

Late
A shift that occurs at a higher speed than normal for a given throttle position.

Shudder
Multiple, rapid jerks usually associated with an oncoming clutch.

Slipping
A noticeable increase in engine speed without an increase in vehicle speed. Usually occurs just after the initial application of a clutch.

Soft
A slow, almost unnoticeable clutch apply.

Surge
A repeating engine-related condition of acceleration and deceleration that is less intense than Shudder.

Tie-up
A condition where two opposing clutches (usually one oncoming and one off-going) are applied at the same time. Gives a braking sensation and/or loss of engine speed.

Noise Conditions

Planetary Gear Noise
A whine related to engine speed and noticeable in a particular transmission range. May be less noticeable or disappear following a transmission upshift.

Pump Noise
A high pitched whine that increases in intensity with increasing engine speed. This noise may occur in any transmission range and with the vehicle moving or stationary.

Torque Converter Noise
A whine usually noticed when the vehicle is stopped and the transmission is in D (Drive) or R (Reverse).Thermostatic Fan Noise

Thermostatic Fan Noise
A normal noise that occurs while climbing a grade under load caused by the engaging/disengaging of the engine cooling fan thermostatic clutch.

Transmission Abbreviations

AC
Alternating Current

DC
Direct Current

DLC
Diagnostic Link Connector

DMM
Digital Multimeter

DTC
Diagnostic Trouble Code

ECT
Engine Coolant Temperature

EMI
Electromagnetic Interference

IGN
Ignition

MIL
Malfunction Indicator Lamp

NC
Normally Closed

NO
Normally Open

OBD
On Board Diagnostic

PCCS
PROM Calibration Configuration System

PNP
Park/Neutral Position

PWM
Pulse Width Modulation

PTO
Power Takeoff

RPM
Revolutions Per Minute

TCC
Torque Converter Clutch

TCM
Transmission Control Module

TFT
Transmission Fluid Temperature

TP
Throttle Position

TPS
Throttle Position Sensor

VCM
Vehicle Control Module

WOT
Wide-Open Throttle

2WD
Two-Wheel Drive

4WD
Four-Wheel Drive