A method for controlling a downshift in an automatic transmission

摘要

A method for controlling a coast down downshift that is produced in an automatic transmission by disengaging an off-going control element and engaging an oncoming control element. A first desired pressure magnitude of the off-going control element 106 and a first desired pressure magnitude of the oncoming control element 106 is determined. The current downshift is executed using said first desired pressure magnitudes. During execution of the current downshift corrections 122, 132 of said first desired pressure magnitudes that occur during the current downshift are determined. A second desired pressure magnitude of the off-going control element 116 and a second desired pressure magnitude of the oncoming control element 126 is determined. Said corrections and the second desired pressure magnitude are used to determine a subsequent desired pressure magnitude of the off-going control element and a subsequent desired pressure magnitude of the oncoming control element. A downshift using said subsequent desired pressure magnitudes is then executed. The said corrections may correct for delay 128 and lash 118 in the downshift.