Transmission Definitions

Transmission Definitions

The following definitions are being provided to establish a common language and assist the user in 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.
- Medium Throttle - Approximately 1/2 of accelerator pedal travel.
- Heavy Throttle - Approximately 3/4 of the accelerator pedal travel.
- Wide Open Throttle (WOT) - Full travel of the accelerator pedal.
- Full Throttle Detent Downshift - A quick apply of the accelerator pedal to its full travel, forcing a downshift.
- Zero Throttle Coast-Down - A full release of the accelerator pedal while the vehicle is in motion and in drive range.
- Engine Braking - A condition where the engine is used to slow the vehicle by manually downshifting during a zero throttle coast-down.

Shift Conditions

- Bump - A sudden and forceful apply of a clutch or band.
- Chuggle - A bucking or jerking condition that may be engine related. 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. This condition could be described as clutch or band engagement not occuring 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" shift.
- Double Bump ("Double Feel") - Two sudden and forceful applies of a clutch or band.
- Early - A condition where the shift occurs before the vehicle has reached a proper speed and tends to labor the engine after the upshift.
- End Pump - A firmer feel at the end of a shift as compared to the feel at the start of a shift. Also defined as "END FEEL" or "SLIP BUMP."
- Firm - A noticeable quick apply of a clutch or band that is considered normal with a medium to heavy throttle shift. Should not be confused with "HARSH" or "ROUGH."
- Flare - A quick increase in engine rpm accompanied 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 to "FIRM." This condition is considered undesirable at any throttle position.
- Hunting - A repeating quick series of upshifting and downshifting 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 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 sensation similar to "CHUGGLE" but more severe and rapid in nature. This condition may be most noticeable during certain ranges of vehicle speed. May also be used to define the condition after converter clutch engagement.
- Slipping - A noticeable increase in engine rpm without a vehicle speed increase. A slip usually occurs during or after initial clutch or band engagement.
- Soft - A slow, almost unnoticeable clutch apply with very little shift feel.
- Surge - A repeating engine related feeling of acceleration and deceleration that is less intense than "CHUGGLE."
- Tie-Up - A condition where two opposing clutches are attempting to apply at the same time causing the engine to labor with a noticeable loss of engine RPM.

Noise Conditions

- Gear Noise - A whine, most noticeable in first gear and reverse, that is related to vehicle speed. A gear noise condition may become less noticeable or go away after an upshift.
- Pump Noise - A high pitch whine that increases in intensity with engine rpm. This condition may also be noticeable in "PARK" and "NEUTRAL" operating ranges with the vehicle stationary.