Transmission - definition

A transmission is a system that transfers power from a vehicle’s power source to the wheels while managing speed and torque. In conventional ICE vehicles, the transmission is typically multi-speed (manual or automatic) and is required because internal combustion engines operate efficiently only within a narrow RPM range. Multiple gears allow the engine to accelerate from rest, cruise efficiently, and deliver power at higher speeds.

In EVs, transmissions are much simpler. Most use a single-speed reduction gearbox because electric motors produce high torque from zero RPM and operate efficiently across a wide speed range, eliminating the need for multiple gears. PHEVs and EREVs combine both concepts: they may use modified multi-speed transmissions or power-split systems to manage power from both the electric motor and the ICE. These transmissions are designed to optimize efficiency, smooth transitions, and energy recovery rather than frequent gear changes.

Related terms: