The present invention provides methods and systems for improving the operation of an automatic transmission for automotive vehicles, particularly automatic transmissions installed by original automobile manufacturers. The methods of the invention employ fluid mechanics and other structural components for modifying signals and responses of the valve body of the original transmissions without making any substantial modifications to the structure of the valve body itself. In one embodiment of the invention, the clearance stroke of a servo-piston is reduced to increase the engagement time resulting in more gradual gear engagement and pressure application at a lower pressure-time ratio. A valve system is provided to rapidly establish a desired system pressure during the clearance stroke, and apply pressure at a controlled rate during the engagement stroke. In other aspects of the invention, downshift is controlled primarily by oil volume and feed hole size, and is not dependent on regulating valves. The method of the present invention significantly reduces the quantity of oil required to operate several sub-systems within the transmission which increases the availability of oil within the system to enable a transmission pump to quickly compensate for abrupt pressure drops through the transmission.