Line pressure optimization in an automatic transmission

摘要

A method is provided for use in a vehicle including an automatic transmission having at least one load carrying friction element, such as clutch, of optimizing the line pressure in the transmission by slipping the weakest friction element by a small amount. The method includes the steps of decreasing the line pressure from a predetermined base pressure to allow for incipient slip across the weakest friction element and then increasing the line pressure to obtain a temporary pressure at which the weakest friction element is no longer slipping. The method also includes the step of further increasing the line pressure from the temporary pressure to obtain an operating line pressure. Preferably, the operating line pressure provides the weakest friction element with additional capacity for transmitting torque without slip for normal driving conditions, i.e. sensed vehicle throttle positions within a predetermined hysteresis band.