A method of operating a drive-train (1) of a motor vehicle, which has a drive aggregate (2), a transmission (3) with a hydrodynamic torque converter (4), an engine brake device (6) and a drive output (5). The engine brake device (6) which is activated when the drive-train (1) is operating in an overdrive mode, during a coasting process, before carrying out an overdrive downshift, when the turbine rotational speed (n_tu) of the torque converter (4) is lower than the engine idling rotational speed (n_mot_LL) of the drive aggregate (2). The engine brake device (6) is deactivated at a point in time chosen such that, when the overdrive downshift is carried out, a load change in the drive-train (1) is avoided.

Systems and methods for operating a hybrid powertrain that includes an engine and a motor/generator are described. The systems and methods adjust torque converter clutch opening responsive to whether or not a motor/generator is available to provide a negative torque to a driveline. Further, the motor/generator and the vehicle's engine are operated to provide a desired amount of driveline braking.

A vehicle system may include a controller configured to increase, after a specified delay, an engagement pressure of a torque converter clutch prior to occurrence of the event to a target pressure that is based on a regenerative braking torque estimate associated with the event such that a portion of energy associated with the event is converted to electricity. The controller may increase the engagement pressure in response to an accelerator pedal release and an expected regenerative braking event.

A vehicle includes a powertrain and a controller. The powertrain includes a transmission torque converter having a bypass clutch disposed between an electric machine and a drive wheel. The controller is programmed to adjust a closed-state torque capacity of the bypass clutch according and in proportion to the greater in absolute value of a negative impeller torque command to the torque converter and a negative regenerative braking torque request.

A braking reduction and transmission control system is implemented in a vehicle or machine having a power source and an automatic transmission connected by a torque converter providing a fluid coupling between a power source output shaft and a transmission input shaft. A lock-up clutch operatively connect to the torque converter is locked when the shafts are rotating at approximately the same speed. The braking reduction and transmission control system unlocks the lock-up clutch when operating conditions of the machine indicate that a transmission downshift will occur, such as when a combination of a brake input device displacement and a machine ground speed compared to a transmission downshift schedule indicate that the downshift will occur. Prior to downshifting the transmission and unlocking the torque converter, the drivetrain assists the service brakes in slowing the machine.

A vehicle system may include a controller configured to increase, after a specified delay, an engagement pressure of a torque converter clutch prior to occurrence of the event to a target pressure that is based on a regenerative braking torque estimate associated with the event such that a portion of energy associated with the event is converted to electricity. The controller may increase the engagement pressure in response to an accelerator pedal release and an expected regenerative braking event.