Abstract: An automatic transmission mechanism having multiple ratio gearing and clutch and brake elements operated by fluid pressure operated servos for changing speed ratio in the transmission and a controller for actuating and releasing the clutches and brakes in response to operating demands determined by sensed variables such as vehicle speed, engine torque, manual valve position, transmission turbine speed, and engine temperature, and means for achieving improved control of a synchronous downshift event by electronically regulating the exhaust pressure from an off-going friction element of the clutch and brake structure, thus controlling the torque-carrying capacity of that off-going element during the downshift interval.

Abstract: An electronic control system for a multiple ratio automotive transmission having pressure operated clutch and brake servos for controlling ratio changes, solenoid operated valves for triggering operation of shift valves in a valve circuit that communicates with the servos, a microprocessor for developing control signals in response to input variables that measure engine torque, engine speed, vehicle speed and a driver-actuated range selector, the shift valves responding to the control signals in accordance with a control strategy that effects controlled response of the shift valves to meet varying road speed, engine torque and road conditions with high quality shift performance.