Abbreviations and Definitions
Transmission Abbreviations and DefinitionsAbbreviations
- PCM - Powertrain Control Module.
- TCC - [1][2]Torque Converter Clutch.
- TP Sensor - Throttle Position Sensor.
- ECT Sensor - Engine Coolant Temperature Sensor.
- VSS - Vehicle Speed Sensor.
- RWD - Rear Wheel Drive.
- 2WD - 2 Wheel Drive.
- 4WD - 4 Wheel Drive.
- PSA - Transmission Fluid Pressure Switch Assembly.
- TTS - Transmission Temperature Sensor
The following definitions and abbreviations are provided to establish a common language for describing transmission related conditions.
Throttle Positions
- Minimum Throttle - the least amount of throttle opening required for an upshift.
- Light Throttle - approximately 1/4 of accelerator pedal travel. (25% Throttle Position)
- Medium Throttle - approximately 1/2 of accelerator pedal travel. (50% Throttle Position)
- Heavy Throttle - approximately 3/4 of accelerator pedal travel. (75% Throttle Position)
- Wide Open Throttle (WOT) - full travel of the accelerator pedal. (100% Throttle Position)
- Full Throttle Detent Downshift - a quick apply of the accelerator pedal to its full travel, forcing a downshift.
- Zero Throttle Coastdown - a full release of the accelerator pedal while the car is in motion and in drive range.
- Engine Braking - a condition where the engine is used to slow the car by manually downshifting during a zero throttle coastdown.
Shift Conditions
- Bump - a sudden and forceful apply of a clutch or band.
- Chuggle - a bucking or jerking may be most noticeable when the converter clutch is engaged; similar to the feel of towing a trailer.
- Delayed - a condition where a shift is expected but does not occur for a period of time. Samples of this could be described as clutch or band engagement that does not occur as quickly as expected during a part throttle or wide open throttle apply of the accelerator or, when manually downshifting to a lower range. Also defined as "LATE" or "EXTENDED".
- Double Bump (Double Feel) - two sudden and forceful applies of a clutch or band.
- Early - a condition where the shift occurs before the car has reached proper speed. Tends to labor the engine after the upshift.
- End Bump - a firmer feel at the end of a shift as compared to the feel at the start of the shift. Also defined as "END FEEL" or "SLIP BUMP".
- Firm - a noticeably quick apply of a clutch or band that is considered normal with a medium to heavy throttle. Should not be confused with "HARSH" or "ROUGH".
- Flare - a quick increase in engine rpm along with a momentary loss of torque. This most generally occurs during a shift. Also defined as "SLIPPING".
- Harsh (Rough) - a more noticeable apply of a clutch or band as compared with "FIRM". This condition is considered undesirable at any throttle position.
- Hunting - a repeating quick series of upshifts and downshifts that causes a noticeable change in engine rpm. An example could be described as a 4-3-4 shift pattern. Also defined as "BUSYNESS".
- Initial Feel - a distinct firmer feel at the start of a shift as compared to the finish of the shift.
- Late - a shift that occurs when the engine is at a higher than normal rpm for a given amount of throttle.
- Shudder - a repeating jerking condition similar to "CHUGGLE" but more severe and rapid. This condition may be most noticeable during certain ranges of car speed.
- Slipping - a noticeable increase in engine rpm without a car speed increase. A slip usually occurs during or after initial clutch or band apply.
- Soft - a slow, almost unnoticeable clutch or band apply with very little shift feel.
- Surge - a repeating engine related condition of acceleration and deceleration that is less intense than "CHUGGLE".
- Tie-Up - a condition where two opposing clutches and/or bands are attempting to apply at the same time causing the engine to labor with a noticeable loss of engine rpm.
Noise Conditions
- Planetary Gear Noise - a whine related to car speed most noticeable in first gear or reverse. Becomes less noticeable after an upshift.
- Pump Noise - a high pitch whine that increases with engine rpm.