Abstract: To reduce shift bump and increase smoothness during shifts, pressure into an on-coming clutch of an automatic transmission is electronically controlled using a turbine speed adaptive strategy. Because of the change in engine speed that accompanies this torque flow path transition, such shifts include a torque phase and an inertia phase. To make the shift smooth, the torque phase is completed quickly by boosting pressure at the beginning of the shift. Just before the torque phase is commpleted, the pressure is lowered so the inertia phase bump is reduced. The end of the torque phase is predicted by monitoring the turbine speed rise since the start of the shift and comparing it with a value which is derived from an adaptive table. During the inertia phase, the pressure is ramped up to complete the shift quickly and smoothly. Ignition spark timing is reduced in the inertia phase to further improve shift feel.

Abstract: A control system for an automatic transmission for an automative vehicle having a torque converter and a combustion engine including a microprocessor that is adapted to establish optimum control pressure levels for fluid pressure operated clutch and brake servos that effect gear ratio changes wherein provision is made for adjusting system pressures to maintain ratio shift quality in accordance with variations in a plurality of control sensor inputs including vehicle deceleration during ratio shifting and changes in the rate of change of converter turbine speed wherein optimum servo pressures are maintained following a ratio shift and during a ratio shift as torque capacity of one servo is reduced in synchronism with a torque capacity increase for a companion servo.