Single-speed reducer

An electric car does not need a gearbox in the usual sense. The motor produces its full torque from a standstill and spins happily to well over 10,000 rpm, so a single fixed ratio covers everything from crawling in a jam to highway speed. What sits between the motor and the wheels is a reducer: typically two gear stages that slow the motor shaft down and multiply its torque by roughly eight to ten times, then a differential that splits the drive between the two wheels.

• The motor shaft carries a small pinion that drives a larger intermediate gear.
• A second pinion on the intermediate shaft drives the big final-drive ring gear bolted to the differential.
• Half-shafts with CV joints take the drive to the wheels.
• There is no clutch: to stop, the motor simply stops; to reverse, it spins the other way; parking uses a locking pawl.

Motor, inverter and reducer are usually built as one unit, sometimes called an e-axle, sitting under the bonnet of a front-driven car like the Nexon.ev or Windsor, or between the rear wheels of a rear-driven one like the Mahindra BE 6. The gears run in a small amount of oil and are rarely serviced. Because the motor can also act as a generator, lifting off the accelerator slows the car through the same gears and sends energy back to the battery.

What you notice: silent, instant response with no gear changes at all, a selector with only D, N, R and P, and, in a two-motor car, a second reducer on the other axle for all-wheel drive. Only a few high-end EVs use two speeds.