CVT

A Continuously Variable Transmission, commonly shortened to CVT, replaces the fixed gear sets found in conventional automatic and manual transmissions with a steel or composite belt or chain riding between two variable-diameter pulleys. By changing the effective diameter of each pulley, the transmission can smoothly vary the drive ratio across a continuous range rather than stepping between a fixed number of discrete gears. This lets the engine operate at or near its most efficient RPM across a wide range of vehicle speeds, since the transmission adjusts the ratio continuously instead of forcing the engine to change speed as the vehicle shifts between gears.

CVTs are widely used in economy cars, crossovers, and hybrid vehicles because they pair well with the efficiency goals of those platforms; keeping the engine near its optimal RPM band improves fuel economy, and the lack of discrete gear changes eliminates the small efficiency losses and mechanical complexity of shift events. Many hybrid vehicles use a variant called a power-split CVT, which blends power from a gasoline engine and one or more electric motors through a planetary gearset rather than a traditional belt-and-pulley design, though the driving characteristic, a stepless, continuously variable ratio, is similar.

The main criticism of CVTs is the driving experience: because engine RPM does not rise and fall with discrete gear changes, occupants can feel or hear the engine hold a steady, elevated RPM during acceleration, an effect sometimes called the rubber-band feel. Manufacturers have addressed this with simulated shift points programmed into the CVT's control software to mimic the feel of a stepped automatic. CVTs also generally have lower torque capacity than stepped automatics, which has historically limited their use in high-power or heavy-duty applications, though pulley and belt technology has improved that ceiling over time.