The present invention provides a method and apparatus for mathematically
calculating an optimal transmission input torque value for the inertia
phase and the torque phase of a ratio change. Engine output is then
altered by an amount necessary to change the actual value of the
transmission input torque to the calculated optimal value of transmission
input torque. The timing of the clutch elements during the power-on skip
through neutral downshift is established by calculating delay periods for
the off-going and on-coming clutches such that a predetermined desired
shift time is met. The power-on skip through neutral downshift is
thereafter adaptively controlled so that aberrations are diagnosed and
corrected during subsequent downshifts. The invention is carried out by
monitoring engine and/or transmission characteristics including input
speed, output speed and shift duration during a downshift and identifying
departures from acceptable patterns. Each type of departure calls for a
particular remedy, and a suitable adjustment is calculated thereafter
implemented by changing one or more initial conditions for the next shift
of the same type.