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Electronic transmissions

Electronic transmissions. Main controls. Shift timing is computer controlled Line pressure is computer controlled which controls shift feel Computer can engage limp in modes for transmission protection Computer can now engage TCC smoother. Why????? .

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Electronic transmissions

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  1. Electronic transmissions

  2. Main controls • Shift timing is computer controlled • Line pressure is computer controlled which controls shift feel • Computer can engage limp in modes for transmission protection • Computer can now engage TCC smoother

  3. Why????? • Electronic controls provide immediate shift control • Shifts are only as firm as necessary • Computer can compensate for normal wear • Valve bodies are less complicated

  4. Computer • Can be separate from or part of engine computer • May be called TCM or transmission control module • Will share many engine sensors through a serial data bus

  5. Inputs • The more information the computer knows, the better it can control shifting • Common info needed from engine • Engine RPM • Engine load • Throttle position • Engine temperature

  6. Inputs continued • Common info needed from trans • Gear shift position • Vehicle speed • Turbine speed • Output shaft speed on 4WD • Transmission temperature

  7. Outputs - Solenoids • Solenoids • Most trans have 3 or 4 in valve body • Will control shift timing, torque converter clutch apply and line pressure • Shift solenoids will be an on/off device • Gears can be accomplished by using combinations of solenoid operation

  8. Shift solenoid failures • Solenoids can stick on or off • If one solenoid sticks (on or off) - transmission may only obtain two gears • If all solenoids fail to operate, trans goes into limp-in mode • Usually only one gear • Fixed high line pressure • No TCC

  9. Outputs continued • Pressure control is obtained by actuating a solenoid with a pulse width modulated signal • PWM is a rapidly pulsing, fixed hertz signal • PWM signals vary only in duty cycle • Solenoid will take the place of TV system • Solenoid may be called force motor

  10. Pressure solenoid failures • If solenoid looses power, usually maximum pressure • If solenoid sticks in low pressure mode, _________ could happen • May set trouble codes

  11. TCC control • Similar as always but will use PWM to engage • Can be monitored for slippage by trans input speed sensor

  12. Adaptive learning • Compensates for normal friction wear • Compensates for different driving habits • Cleared when computer keep alive power lost

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