They haven't a transmission in the classical sense and they are of course without clutch technology. While internal combustion engines require multiple gears with different ratios for power output, electric motors produce a consistent amount of torque at any given RPM within a specific range. Electric motors deliver power instantly, meaning, the process of building up torque through revving as in internal combustion engines is unnecessary. Car manufacturers incorporate carefully calculated gear ratios to maximize efficiency for the electric motor without having to switch through gears.