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

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

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

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

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

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

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

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

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

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