A transmission system for a vehicle comprises a first partial transmission with a first controllable clutch and a second partial transmission with a second controllable clutch each forming a respective transmission path between an input and a common output (to), the first and the second controllable clutches having first and second actuators, respectively, to control an operational state of said controllable clutches. A controller is provided to control the first and the second actuators, the controller being configured to selectively assume one of a plurality of control modes. These include amongst others a safety control mode which is selected upon detecting that a value of an acceleration of the vehicle is lower than a negative threshold value.

A hydraulic control circuit includes: a shift valve configured to be switched between a state of supplying oil pressure to a clearance adjusting chamber of an LR brake and a state of discharging the oil pressure from the clearance adjusting chamber of the LR brake; and a linear SV configured to control the oil pressure supplied to a pressing chamber of the LR brake. The hydraulic control circuit further includes a source pressure oil passage through which oil pressure equal to the oil pressure supplied from the shift valve to the clearance adjusting chamber is supplied to a source pressure port a of the linear SV. By discharging the oil pressure in the clearance adjusting chamber at the time of opening malfunction of the linear SV, the oil pressure in the pressing chamber is also discharged through a drain port of the shift valve.

An electro-hydraulic control system for a multispeed transmission having a plurality of torque-transmitting mechanisms includes a controller for operably controlling the transmission, a fluid source for supplying hydraulic fluid, and a plurality of torque-transmitting mechanisms being operably selected between an applied and an unapplied state to achieve a plurality of ranges including at least one reverse, a neutral, and a plurality of forward ranges. The system includes a plurality of trim systems having pressure control solenoids and trim valves. The system may also include one or more shift valves disposed in fluid communication with the fluid source and being capable of moving between stroked and de-stroked positions. In any given range, only two of the plurality of torque-transmitting mechanisms may be applied. Moreover, three of the plurality of pressure control solenoids are normally high solenoids, and the remaining solenoids are normally low solenoids.

A method of controlling an automated transmission with positioning cylinders (6, 8, 20) controlled by shift valves or venting valves (10, 12, 16, 18, 22, 24). At least one cut-off valve (4) is positioned in front of the shift or venting valves and a control device controls the valves while pressure pipes, which follow the cut-off valve (4), are connected with one another following the cut-off valve (4). Due to the fact that the cut-off valve (4), for reasons of design simplicity and cost, is generally designed as a simple 2/2 way valve which only allows pressure increase but not pressure reduction, the method provides control of the shift valves or ventilation or venting valves (16, 18), of a non activated positioning cylinder (8), so that the pressure pipe system is connected with an outflow pipe (14) for a pressure reduction in the pressure pipe system (30, 32, 34).

A transmission control system of a vehicle includes an estimated acceleration module and a pressure control module. The estimated acceleration module determines an estimated longitudinal acceleration of the vehicle based on a force at axles of the vehicle corresponding to engine torque, a braking force imposed by mechanical brakes of the vehicle, an aerodynamic drag force of the vehicle, and a road load force imposed on the vehicle by contact between tires of the vehicle and a road surface. The pressure control module, when a measured longitudinal acceleration of the vehicle is negative and the estimated longitudinal acceleration is greater than the measured longitudinal acceleration of the vehicle, adjusts transmission fluid pressure applied to one or more clutches of the transmission and shifts the transmission to neutral.

In a method for operating a transmission device, a pressure test is carried out when switching from a standby mode to a power saving mode. When executing the pressure test the gear selector valves of the gear selectors of the transmission device are activated to assume their neutral position, and a shifting valve is activated to assume an operating position in which a flow connection between a common feed line for the gear selectors and a pressure source is cut. Subsequently, the gear selector valve of at least one of the gear selectors is activated to assume a shift position, and a position of the gear selector piston of the at least one gear selector is determined over a specific time period. The presence of a malfunction of the shifting valve is recognized when the position of the gear selector piston changes during the specific time period.

A shift system includes a shifter including a first switch, a second switch, and an interlock switch and being operable between a plurality of gear states. A controller is communicatively coupled with the shifter to receive signals that correspond to each of the first switch, the second switch, and the interlock switch. The controller includes a diagnostic counter that includes a passing criteria and a predetermined diagnostic threshold and is configured to adjust the diagnostic counter based on at least one of the signals received from the shifter being inconsistent with the others of the signals received.