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 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 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 a band.

Chuggle: a bucking or jerking. This condition may be most noticeable when the converter clutch is engaged. It is similar to the feel of a towing trailer.

Delayed: a condition where a shift is expected but does not occur for a period of time. This could be described as a 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 during manual downshifting to a lower range. This term is also defined as LATE or EXTENDED.

Double Bump (Double Feel): two sudden and forceful applies of a clutch or a band.

Early: a condition where the shift occurs before the car has reached proper speed. This condition tends to labor the engine after the upshift.

End Bump: a firmer feel at the end of a shift than at the start of the shift. This is 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. This apply 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. This condition is also defined as SLIPPING.

Harsh (Rough): a more noticeable apply of a clutch or band than 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, such as a 4-3-4 shift pattern. This condition is also defined as BUSYNESS.

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

Late: a shift that occurs when the engine's RPM is higher than normal 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 clutch 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

Drive Link Noise: a whine or growl that increases or fades with engine RPM. This noise is most noticeable under a light throttle acceleration, or in Park or Neutral with the car stationary.

Final Drive Noise: a hum related to car speed. This noise is most noticeable under a light throttle acceleration or zero throttle coastdown.

Planetary Gear Noise: a whine related to car speed. This noise is most noticeable in First gear, Second gear, Fourth gear, or Reverse. The condition becomes less noticeable after an upshift.

Pump Noise: a high pitched whine that increases with engine RPM and may be affected by modulated line pressure boost.

Torque Converter: a whine usually noticed when a vehicle is stopped and the transmission is in Drive or Reverse. The noise will increase with engine RPM. Refer to the Torque Converter Evaluation portion of Torque Converter Clutch Diagnosis

Transmission Abbreviations

A/C:  Air Conditioning

AC: Alternating Current

A/T ISS: Transmission Input Speed Sensor

A/T OSS: Vehicle Speed Sensor

CKT: Circuit

DC: Direct Current

DLC: Diagnostic Link Connector

DMM: Digital Multimeter

DTC: Diagnostic Trouble Code

ECT Sensor: Engine Coolant Temperature Sensor

EGR: Exhaust Gas Recirculation

MAP: Manifold Absolute Pressure

MIL: Malfunction Indicator Lamp

NC: Normally Closed

NO: Normally Open

OBD: On Board Diagnostics

PCM: Powertrain Control Module

PCS: Pressure Control Solenoid

PM: Permanent Magnet

PWM: Pulse Width Modulated

RPM: Revolutions Per Minute

TCC: Torque Converter Clutch

TCM: Transmission Control Module

TFP Val. Position Sw.: Automatic Transmission Fluid Pressure Manual Valve Position Switch

TFT Sensor: Automatic Transmission Fluid Temperature Sensor

TP Sensor: Throttle Position Sensor

WOT: Wide Open Throttle