Downshift controls using measured output torque

A method for controlling a transmission downshift during a coasting drive condition where a vehicle continues to move forward while both an acceleration pedal and a brake pedal are released, comprising:

• determining initial output torque before the downshift;
• directly measuring initial input speed before the downshift;
• starting the downshift by initiating offgoing element pressure reduction and stroking an oncoming element;
• establishing maximum and minimum values of output torque and a reference change in input speed for the downshift;
• measuring output torque and input speed;
• computing a change in output torque from the initial output torque and a change in input speed from the initial input speed;
• reducing offgoing element pressure to allow an offgoing clutch to slip;
• further reducing offgoing element pressure, provided the change in input speed exceeds the reference change in input speed;
• using closed loop control based on output torque and the change in output torque to adjust oncoming element pressure such that output torque is between its maximum and minimum values without allowing on-coming clutch to securely engage and without allowing the downshift to complete as long as completion of downshift is not desired;
• completing the downshift by increasing oncoming element pressure when said completion is desired.