Abstract: An automatic transmission control system having gearing that establishes multiple forward driving ratios and a reverse ratio as well as a neutral mode, an electrohydraulic control valve circuit for controlling the application and release of clutch and brake elements for the transmission gearing, a driver-controlled range selector for transmitting operator commands to shift control logic, and a failure mode management circuit that monitors the shift control logic and the response of the transmission system to operator commands, as well as the transmission range selector signals delivered to the shift control logic whereby multiple control redundancies in the electronic range control system ensure that system failures and component failures develop an error signal to alert the driver of possible malfunctions during the range selection period.

Abstract: A check valve for use in an hydraulic control circuit includes separator plates each having an orifice of predetermined size and a ball retained between the separator plates, adapted to close one of the orifices and to open a port and parallel passages communicating with a chamber in which a ball is retained. The ball chamber is in continual communication with the orifice that is not closed by the ball.

Abstract: An electronically actuated park control system for an automatic transmission for a wheeled vehicle including a transmission range selection control assembly that sends to a powertrain control module a park signal, the module being adapted to deliver an output signal to a park controller circuit for actuating electric actuator motors which activate a mechanical transmission park mechanism, the motors having position feedback monitoring features as the transmission park mechanism is engaged or disengaged, the controller and the park controller circuit having inherent design redundancies as well as independent watchdog circuitry that ensure that transmission park release or park application responds precisely to transmission range selector requests by the driver.