Overdrive Range, 4-3 Downshift - Torque Converter Clutch Not Applied (With Touch Activated Power): Notes
WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.
When the transmission is operating in Fourth gear, a 4-3 downshift will occur if there is a significant change (increase) in the throttle position or if the load on the engine is increased. When the 4-3 downshift occurs, the torque converter clutch will release prior to the shift occurring which results in the following changes in the hydraulic system: