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