A method and transmission control unit configured to improve shift event performance in a vehicle with an automatic transmission by determining a vent time for release of a clutch assembly in a transmission of a vehicle. The vehicle must be stopped and a gear selector in the vehicle must be set to a drive condition. If these conditions are met, the clutch assembly is vented. The vent time from when venting begins to when a turbine (or input shift) speed of the transmission rises is tracked. Once the turbine speed of the transmission rises, the clutch assembly is reapplied. The clutch assembly vent time is set based on the tracked vent time.