Abstract: An automatic transmission of a vehicle including a speed change gear mechanism including rotary members such as gears and gear carriers and hydraulically operated friction engaging means and adapted to provide various speed stages according to selective engagement and disengagement of the friction engaging means is controlled by such steps as detecting rotation speed of at least one of the rotary members during a shifting between the speed stages, changing hydraulic pressure of at least one of the friction engaging means during a first phase of the speed stage shifting so as to make the rotation speed of the one rotary member follow a first change performance curve calculated according to a first feedback control program, and changing the hydraulic pressure of the one friction engaging means during a second phase of the speed stage shifting so as to make the rotation speed of the one rotary member follow a second change performance curve calculated according to a second feedback control program in continuity

Abstract: In a method for downshifting of an automatic transmission of a vehicle according to an increase of throttle opening, a delay time between a judgement of a requirement of downshifting of the transmission and the execution of the downshifting is determined to base upon change rate of the throttle opening, and when the delay time was counted up, a requirement of downshifting of the transmission is again judged before the execution of any downshifting.

Abstract: A hydraulic breather for a valve body in an automatic transmission, in which is disposed hydraulic equipment, for example, linear solenoid valves. The breather separates oil in the oil pan from the oil in the hydraulilc equipment when the automatic transmission is at work while allowing clean oil from the oil pan to enter the hydraulic equipment when the automatic transmission is at rest. The breating hole is provided in the form of an oil passage extending from hydraulic equipment within the valve body and includes an open-end section disposed in an upper part of the valve body. The open-end is located at a point higher than the working oil level in the automatic transmission. When the automatic transmission is at work, oil in the oil pan is used to lubricate, so the oil level is at its lowest level and the open-end section is above that oil level and thereby connects with air space in the valve body.

Abstract: In a speed stage shifting of an automatic transmission in a vehicle by engagement of a hydraulically operated friction engaging means through supply of a hydraulic fluid to the friction engaging means via a passage means including an accumulator operative with support by a back pressure, the back pressure is first maintained at an incipient pressure level, and is increased from the incipient pressure level toward a regular pressure level upon the lapse of a delay time from the detection of a transition phase when the transition phase starts before the lapse of a guard time or upon the lapse of the guard time when the guard time lapses before the start of the transition phase.

Abstract: In the control of engine output torque for its temporary reduction for change-over of speed stages of an automatic transmission in a vehicle, recovery of the temporarily reduced engine output torque is started when a monitored rotational speed of a rotary member of the automatic transmission approaches its final value to be attained after the completion of the change-over of speed stages across a predetermined border value, and during the recovery the reduction of engine output torque is periodically adjusted in accordance with a difference between a current monitored rotational speed of the rotary member and its final due value so that a current amount of the reduction of engine output torque is decreased along with decrease of the above-mentioned difference.