Microprocessor-based control technology has found widespread application in automotive engineering. Nissan has been studying the effective application of a microprocessor to an automatic transmission system. A new microprocessor controlled automatic transmission has been introduced to meet the demands for better fuel economy and driveability.The microprocessor controls the optimum operation of the lockup clutch in all four speeds which provides improved fuel economy and driving performance. Engagement and disengagement of the clutch are carried out precisely without degrading shift quality. The other controls for down-shifting while coasting and automatic selection of the shift schedule also improve driveability. These controls are the first of their kind to be applied in the world.