Final answer:
A driver would turn off transmission overdrive in a 2021 NV200 to gain more torque and control while driving up steep inclines, towing, or in challenging driving conditions, even though overdrive generally promotes better fuel economy and reduced emissions.
Step-by-step explanation:
A driver might want to turn off the transmission overdrive in a 2021 NV200 for several reasons, particularly when more torque is needed such as driving up a steep incline, towing, or while driving in conditions that require lower gears. Overdrive is a gear in the transmission that is less than a 1:1 ratio with the engine. When engaged, it reduces the engine's RPM, leading to better fuel economy and less wear. However, in situations requiring more power and control, turning off overdrive allows the engine to run at higher RPMs, enabling more torque and better vehicle control.
Modern transmission technologies such as dual clutch transmissions (DCTs) and continuously variable transmissions (CVTs) are designed to improve fuel economy and reduce CO₂ emissions by optimizing shift points for efficiency. Yet, despite the efficiency benefits of overdrive and advanced transmission systems, there are driving scenarios where it is beneficial to disable these features for enhanced performance and handling.