Transmission types, how they work, and the differences between ICE, hybrid and electric cars
The transmission carries torque from the engine or electric motor to the wheels and changes it depending on speed and load. A clutch or torque converter smoothly connects the powertrain to the gearbox, the gearbox's gears change the ratio, and the differential lets the wheels of one axle spin at different speeds through a turn. Transmission design differs greatly between ICE cars and EVs — the latter usually don't need multiple gears at all.
From a manual gearbox to a single-speed EV reduction gear
The driver selects the gear with a lever, while the clutch pedal briefly interrupts power flow during the shift. The simplest, most reliable and easiest to repair design, but it demands skill and constant driver involvement.
Components
A torque converter replaces the mechanical clutch, smoothly transmitting torque through a fluid coupling, while planetary gear sets shift automatically without interrupting power. Comfortable in city driving, but more complex and heavier than a manual.
Components
Two independent clutches handle even and odd gears, so the next gear is pre-selected and engages almost without interrupting power. Faster than a classic automatic, but demanding on cooling and maintenance quality.
Components
A metal belt or chain transfers torque between two variable-diameter conical pulleys, delivering smooth, stepless ratio changes with no perceptible shift shock.
Components
An electric motor produces torque across a wide speed range, so an EV only needs a single reduction gear instead of a multi-speed gearbox. Simpler, lighter and more reliable than any stepped transmission.
Components
The more complex the powertrain, the more complex the transmission
An internal combustion engine produces torque over a narrow speed range, so it needs a gearbox with 5–8 gears to work efficiently both at launch and on the highway. A clutch or torque converter is essential for a smooth start from rest.
Hybrid transmissions often combine a regular gearbox with one or two electric motors, or use a planetary mechanism with no discrete gears at all (e-CVT), where the combined engine and motor speeds set the effective ratio.
An electric motor doesn't need gear changes — a single fixed reduction gear is enough. This makes an EV's transmission far simpler, lighter and more reliable, and removes the clutch and its maintenance entirely.
The core elements shared by most transmissions
Click a node to see its description in the cards below
Connects and disconnects the engine from the gearbox, allowing smooth starts and shock-free gear changes.
Pairs of differently sized gears change the ratio, letting the engine's power be used efficiently at any speed.
Carries torque from the gearbox to the front or rear axle, with joints that compensate for suspension movement.
Splits torque between the left and right wheels, letting them spin at different speeds through a turn.
Carry torque from the differential to the wheels; constant-velocity (CV) joints let the shaft flex with suspension travel and steering angle.
The sealed casing that holds the gears, shafts and oil bath — keeps out dirt and retains lubrication.