What causes a transmision to slip in low gears

SOURCE: ford taurus will not shift from low gear

I have a 2001 ford taurus and i have transmission fluid leaking on ground when it runs. i was driving it today and it would not shift gears. Then when i got home i saw transmission fuild in the ground.

Marvin

• 85242 Answers
• Posted on Mar 24, 2009

SOURCE: 2002 Ford Explorer with 5R55W transmission: How

I can't find any reference to an adjustment in the overhaul manual, so i will assume this means no adj ness. or provided for.

SOURCE: 1999 ford expedition - transmission slip?

the flashing O/D light usually means you have a bad speed sensor that sends speed info to the engine & trans computer.

Vehicle Speed Sensor The vehicle speed sensor (VSS) (Figure 42) is a variable reluctance or Hall-effect sensor that generates a waveform with a frequency that is proportional to the speed of the vehicle. If the vehicle is moving at a relatively low velocity, the sensor produces a signal with a low frequency. As the vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling and torque converter clutch scheduling.
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Vehicle Speed Sensor The vehicle speed sensor (VSS) (Figure 42) is a variable reluctance or Hall-effect sensor that generates a waveform with a frequency that is proportional to the speed of the vehicle. If the vehicle is moving at a relatively low velocity, the sensor produces a signal with a low frequency. As the vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling and torque converter clutch scheduling.

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Some trans use an OSS, Output Shaft Sensor instead of a VSS. Depends on which trans you have, 4R100 or 4R70W

Transmission Control Switch (TCS) and Transmission Control Indicator Lamp (TCIL)
The transmission control switch (TCS) is a momentary contact switch. When the switch is pressed, a signal is sent to the powertrain control module (PCM) to allow automatic shifts from first through fourth gears or first through third gears only. The PCM energizes the transmission control indicator lamp (TCIL) when the switch is off.

The TCIL indicates overdrive cancel mode activated (lamp on) and electronic pressure control (EPC) circuit shorted (lamp flashing) or monitored sensor failure.

Output Shaft Speed (OSS) Sensor
The output shaft speed (OSS) sensor is a magnetic pickup, located at the output shaft ring gear, that sends a signal to the powertrain control module (PCM) to indicate transmission output shaft speed. The OSS is used for torque converter clutch control, shift scheduling and to determine electronic pressure control.

SOURCE: 92 thunderbird transmission slipping, its about a

Absolutely; Automatic transmissions will slip for a number of factors but the the #1 cause is low fluid level closely followed by very old and brown fluid. Recomended fluid is MerconDexronII. Best of luck.
Greg

SOURCE: we put another transmission in a 95 windstar and

The gear is a bad one too. go for a new transmission please.