Override do not downshift gears, read previous discussion on this topic. As long as shifting gear whiling going downhill or uphill in auto transmission that are coming in todays car causes no problems. But auto transaxle still has a clutch, but its not like the one in manual cars where gears are actually held(clutched) by clutch. In older cars the auto transaxle had a tendency to get stuck in case of extreme situations like, going uphill and suddenly shifting to upper gear or lower gear. But in these older transmissions too there is a button to get the gear unstuck in such situations.