Line pressure control arrangement for automotive automatic transmission

Abstract

When a shift command is issued the line pressure is dropped to a first low level until such time as the inertia phase of the shift begins. From this time the level of line pressure is raised and maintained at a second higher level until the end of the inertia phase. During the final stage of the shift, the level of line pressure is again lowered. A spike in the transmission torque output when tends to occur at the beginning of the inertia phase is attenuated, the level of torque which is transmitted during the inertia phase is elevated and spikes which tend to be produced by the final engagement are reduced by the temporarily lowered final stage line pressure level.