Abstract: A four wheel drive torque transfer mechanism with a hydraulic control system is switchable between two wheel drive and four wheel drive during running of a vehicle having an automatic transmission. A reducer permits direct coupling or reduced speed ratio drives. A parking gear associating with the transfer device requires only small modification to the conventional parking mechanism. The hydraulic control system automatically actuates the reducer to provide a reduced speed-high torque output when a governor output responsive to vehicle speed, falls below a predetermined level.

Abstract: A control apparatus for a torque converter direct coupling clutch in an automatic transmission of a type which permits the shift pattern selectively to be switched over between the three forward speed shift ranges and four forward speed shift ranges according to the desire of a car driver, wherein the improved control apparatus controls the torque converter direct coupling clutch so as to be engaged at the highest speed gear ratio (shift range) in each shift pattern gear ranges.

Abstract: A system for controlling the hydraulic pressure of a hydraulic control circuit of an automatic, variable speed transmission during a shift operation is provided. The hydraulic control circuit includes a plurality of hydraulic pressure control valves, a plurality of flow path switching means and a plurality of solenoid valves for controlling the engagement and disengagement of clutches and brakes in the transmission. The energization of the solenoid valves disposed in the hydraulic control circuit is controlled by an electronic system, which comprises a large scale integrated semiconductor logic unit, a semiconductor read-only memory, a semiconductor read-write memory and as required, input/output ports.

Abstract: A strainer for use on a valve body of an automatic transmission includes an enlarged filter area and is located in an oil pan under the valve body. A strainer divides the oil pan into upper and lower chambers and has a central tube connected with a suction port of the valve body. Fluid discharged into the upper chamber of the oil pan flows down to the lower chamber through the enlarged filtering area of the strainer and is sucked into the valve body through the centrally located tube.

Abstract: A device for controlling a lock-up clutch in an automatic transmission having a lock-up clutch equipped fluid torque converter according to this invention comprises a transient release valve which receives pressurized input oil through a hydraulic passage connected to hydraulic servo means incorporated in the transmission, said transient release valve outputting pressured oil when the pressure of the input oil is higher than preset value, and a lock-up shift valve which receives the pressurized oil from the transient release valve, said lock-up shift valve being adapted for engaging the lock-up clutch when the output pressure is higher than a predetermined value and disengaging it when the pressure is lower than the predetermined value whereby the lock-up clutch is controlled by utilizing variations in hydraulic pressure supplied to the hydraulic servo means.

Abstract: A governor hydraulic pressure supply apparatus is provided for use with the vehicle automatic transmission system and includes a governor valve mounted on a rotary output shaft from the automatic transmission, the output shaft having an internal input fluid line for supplying a line pressure to the governor valve and an internal output fluid line receiving a governor pressure from the governor valve, and the governor valve body having an internal input fluid line to be connected to the input line from the output shaft and an internal governor pressure output line to be connected to the output line in the shaft, wherein the joined faces between the governor valve and output shaft at which the fluid lines are respectively connected with each other are brought in close contact with each other by tightening the two element by means of a tightening bolt adjacent to the joined faces, thereby preventing fluid leak from the faces.

Abstract: An automatic transmission which is provided which has a transfer device between the speed change gears and an overdrive, said transfer device having an output gear which engages an input gear of a differential gear coaxially connected to an output shaft of the speed change gears.

Abstract: In an hydraulic control system for an automatic transmission of a vehicle, when a low range frictional engagement mechanism is engaged in response to shift-down operation of the transmission, a flow regulator valve serves to steplessly regulate flow of fluid from a source of line pressure to the low range frictional engagement mechanism in accordance with changes of travel speed of the vehicle.

Abstract: An accumulator for a hydraulic control system of frictional engagement mechanisms comprises a housing with a stepped bore, a first stepped piston reciprocable within the bore to form a back pressure chamber communicated with a source of line pressure, a second piston reciprocable within the first piston in a predetermind stroke to form an accumulation chamber communicated with the line pressure source, and a spring for biasing the second piston toward the accumulation chamber. In the initial stage, only the second piston is retracted against biasing force of the spring to modulate the line pressure acting on the frictional engagement mechanisms and is engaged at its retracted stroke end with the first piston. Subsequently, the first piston is retracted together with the second piston against the biasing force and the pressure in the back pressure chamber to further modulate the line pressure.