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 coast down
Closed Throttle Coast Down: 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 - also 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 cause 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 occurring 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 2 opposing clutches, usually 1 oncoming and 1 offgoing, are applied at the same time - giving 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 - 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: 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
ECM: Engine Control Module
ECT: Engine Coolant Temperature
EMI: Electromagnetic Interference
IGN: Ignition
IMS: Internal Mode Switch
MIL: Malfunction Indicator Lamp
NC: Normally Closed
NO: Normally Open
OBD: On Board Diagnostic
PCS: Pressure Control Solenoid
PS: Pressure Switch
PTO: Power Take-Off
RPM: Revolutions Per Minute
SS: Shift Solenoid
TCC: Torque Converter Clutch
TCM: Transmission Control Module
TFT: Transmission Fluid Temperature
TP: Throttle Position
TPS: Throttle Position Sensor
VBS: Variable Bleed Solenoid
WOT: Wide-Open Throttle
2WD: Two-Wheel Drive
4WD: Four-Wheel Drive