For normal driving, most automatic vehicles are designed to select the appropriate gears with the transmission in its usual drive setting. Overdrive allows lower engine speed while cruising when conditions permit.
Towing, steep grades, or repeated shifting between gears may call for a tow mode, overdrive cancellation, or another setting specified by the manufacturer. The correct choice depends on your vehicle and load.
If the transmission repeatedly hunts between gears during ordinary driving around Bellevue, contact Certified Transmission. A mode change should not be used to hide a developing shifting problem.