Abstract: An automatic transmission includes a transmission mechanism providing a high speed gear ratio and a low speed gear ratio, a hydraulic control circuit having a cutback device settable in one of a cutback execution state and a cutback suspension state, a primary control device for setting the cutback device in the cutback execution state when the gear ratio is a low speed, and setting the cutback device in the cutback suspension state when the gear ratio is a high speed, a secondary control device for setting the cutback device in the cutback suspension state when the gear ratio is a high speed, and a selection device for selecting the primary control device when the oil temperature is lower than a predetermined value, and selecting the secondary control device when the oil temperature is higher than the predetermined value.

Abstract: An automatic transmission includes a hydraulic control circuit for developing coupling pressure to the friction coupling member, the hydraulic control circuit having a regulator device for regulating the coupling pressure and a solenoid valve for controlling the regulator device, a hydraulic pressure sensor device for detecting hydraulic pressure in connection with the coupling pressure, an actuator device for actuating the solenoid valve in a range between the opening position and the closing position to change the control amount of the solenoid valve when the vehicle is in a predetermined state, a memory device for storing a characteristic relationship between detected hydraulic pressures and changed control amounts, and a control device for controlling the solenoid valve based on the characteristic relationship so that the regulator device regulates the coupling pressure to a desired value.

Abstract: An automatic transmission includes transmission mechanism having a friction coupling member for enabling engine brake, and a hydraulic control circuit having a pressure regulator valve for feeding a coupling pressure to the friction coupling member and a cutback valve for reducing the coupling pressure. This automatic transmission further has a cutback valve control device for suspending the cutback in a particular gear ratio in the engine brake enable range. Accordingly, in the engine brake enable range which requires a higher coupling pressure, a sufficient coupling pressure can be assured by suspending the cutback.