Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Acronyms and Definitions: Transmissions
- The first character, a number, is the number of forward gears.
- The second character, either the letter "F" or "R," represents front (transaxle) or rear (transmission) wheel drive.
- The next set of characters, a grouping of numbers, represents the design torque capacity of the transmission/transaxle (for example, "27" represents 270ft./lbs. in the 4F27E transaxle).
- The last character, if used, is one of the following:
- "E" for electronic shift
- "N" for non-synchronous shift
- "S" for synchronous shift
- "W" for wide ratio
4F27E : Also known as the FN Focus automatic transmission.
4F44E : Formerly known as the CD4E.
4F46S : Formerly known as the AX4S and regular-duty AXOD-E.
4F50N : Formerly known as the AX4N and heavy-duty AXOD-E.
4R44E : Formerly known as A4LD for 3.0L applications.
4R55E : Formerly known as A4LD for 4.0L applications.
4R70W : Formerly known as AOD-E.
4R100 : Formerly known as E4OD.
5R44E : Formerly known as A5LD for 3.0L applications.
5R55E : Formerly known as A5LD for 4.0L applications.
5R55N : Lincoln LS automatic transmission.
5R55W : Wide-ratio truck transmission.
4x4L : 4x4 Low.
A/T : Automatic Transmission.
CCS : Coast Clutch Solenoid.
CCSF : Coast Clutch Solenoid Fault. Displays a YES if fault exists.
EPC, EPC1, EPC2 : Electronic Pressure Control.
EPCV : Electronic Pressure Control Volts.
ESS : Electronic Shift Scheduling.
HCDSS : High Clutch Drum Speed Sensor. PCM input from the 4R44E and 4R55E.
ISS : Intermediate/Input Shaft Speed Sensor.
M5OD : Manual 5-Speed transmission with overdrive (RWD).
M/T : Manual Transmission/Transaxle.
NPS : Neutral Pressure Switch or its signal input to the PCM.
OCS : Overdrive Cancel Switch.
OSS : Output Shaft Speed. Indicates rotational speed of the transmission output shaft.
PNP : Park/Neutral Position switch. Also known as Neutral Drive Switch (NDS), Neutral Gear Switch (NGS), and Transmission Switch Neutral (TSN).
REVERSE or REV : Transmission Reverse Switch Input.
SIL : Shift Indicator Lamp. A lamp that indicates the preferred shift points on select manual transmission/transaxle vehicles.
SS1/SS2/SS3 : Shift solenoids. Devices that control the shifting in an automatic transmission.
TCC/TCCH : Torque Converter Clutch. When energized, causes a mechanical engagement and disengagement of the Torque Converter Clutch.
TCIL : Transmission Control Indicator Lamp. Indicates that the TCS has been activated.
TCS : Transmission Control Switch. Modifies the operation of electronically controlled transmissions.
Torque converter : A device which by its design multiplies the torque in a fluid coupling between an engine and transmission/transaxle.
TFT : Transmission Fluid Temperature. Indicates temperature of transmission fluid.
Transaxle : A device consisting of a transmission and axle drive gears assembled in the same case. Front-wheel drive applications.
Transmission : A device which selectively increases or decreases the ratio of relative rotation between its input and output shafts. Rear-wheel drive applications.
TR, TR1, TR2, TR3, TR4 : Transmission Range. The range in which the transmission is operating.
TR Sensor : Formerly known as Manual Lever Position Sensor (MLPS). Provides information to the PCM on the transmission range selector position.
TR V : Transmission Range Voltage.
TSS : Turbine Shaft Speed. Indicates rotational speed of the transmission turbine shaft.
VSS : Vehicle Speed Sensor. A magnetic pickup device that generates an AC signal that is proportional to vehicle speed.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.