Abstract: A vehicular automatic transmission control system comprising: a hydraulic control circuit including a hydraulic pressure source, a pressure regulator valve for producing a line pressure by regulating the oil pressure supplied from the pressure source, a number of shift valves for selectively engaging and releasing friction members of the automatic transmission according to operating conditions of a vehicle such as vehicle speed and throttle opening rate, and a solenoid valve blocking switching operation of a highest shift gear toward a highest gear position of the transmission; and an electronic control circuit for controlling on- and off-ranges of the solenoid valve, including a manual mode switch for setting the control either in a highest speed non-cancel mode permitting shifts to the highest gear position or a highest speed cancel mode inhibiting shifts to the highest gear position and forcibly effecting a downshift when selected during operation in the highest gear position, and a vehicle speed sensor; c

Abstract: A hydraulic servo for friction coupling devices of automatic transmissions, the hydraulic servo comprising: an annular drum including outer and inner cylinders and a side wall connecting the two cylinders together and mounted fixedly or rotatably within an automatic transmission case; an intermediate cylinder mounted concentrically in a predetermined position between the outer and inner cylinders of the drum; a return biasing means located between the intermediate and inner cylinders; and a connecting member securely connecting the return biasing means to a piston.

Abstract: A four-wheel drive automatic transmission primarily consisting of an automatic transmission having a transmission case, a transmission gear mounted in the transmission case and an automatic transmission hydraulic control unit including a transmission valve body secured to the bottom surface of the transmission case; and a four-wheel drive transfer having a transfer case, a transfer unit mounted in the transfer case and a transfer hydraulic control unit including a transfer valve body secured to the bottom surface of the transfer case. The automatic transmission hydraulic control unit and the transfer hydraulic control unit communicate with each other by oil passages cast in the transmission case and in the transfer case.

Abstract: A lock-up clutch controller for the fluid coupling of an automotive automatic transmission, capable of making a lock-up clutch provided in the fluid coupling for directly coupling the input shaft and the output shaft of the fluid coupling engage or disengage smoothly responsive to an electric duty signal applied to a lock-up operation control solenoid valve. The lock-up clutch controller includes, as essential components, a lock-up clutch relay valve (a spool valve), a lock-up clutch control valve (a spool valve) and the lock-up operation control solenoid valve which operates in accordance with an electrical duty ratio signal to control the lock-up relay valve and the lock-up operation control valve so that the working fluid is supplied to the fluid coupling or the fluid coupling is drained appropriately for the smooth engagement and disengagement of the lock-up clutch.

Abstract: A one-way clutch biasing means for an automatic transmission, comprising: an inner spline formed on a one-way clutch retaining member; an outer spline formed on the outer race of the one-way clutch and loosely meshed with the inner spline; and a resilient member fitted between a side wall surface of the inner spline of the retaining member and an opposing side wall surface of the outer spline of the outer race to urge the outer race constantly in the locking direction of the one-way clutch.

Abstract: A stepless automatic transmission for a motor vehicle includes a V-belt type stepless transmission mechanism having input and output pulleys mounted respectively on input and output shafts, each pulley being provided with a hydraulic servo for varying the effective diameter thereof, and a V-belt linking the input and output pulleys to transmit power therebetween, in combination with a forward/reverse change-over mechanism and a coupler such as a fluid coupling, centrifugal clutch or friction clutch, and a hydraulic control system.