Porsche revealed its 2020 Taycan electric car Wednesday and at last confirmed one long-rumored detail: that it would have a two-speed gearbox for the rear wheels.
The sports-car maker has said that the low gear is one of the secrets to consistency in the Taycan’s consistent off-the-line launches and reproducibility in acceleration runs—just 2.6 seconds to 60 mph, which Porsche says can be repeated ten or more times.
2020 Porsche Taycan preview
In combination with the Taycan’s 800-volt architecture, it not only helps put down more wheel torque but also helps the rear motor (the bigger of the two) and power electronics keep their cool.
The top gear of the two ratios matches the gearing for the motor driving the front wheels—so at higher cruising speeds the two motors are spinning at roughly the same speed. A dog clutch—meaning not a slippy clutch, just fully on or fully off—can decouple the motor from the gearbox completely, allowing the Taycan to run as a front-wheel-drive car in its Range mode, or during very light loads.
In dual-motor versions of the Model S, Tesla has long used a setup in which the motors were geared differently, accomplishing some of the same high-speed efficiency goals. The original Tesla Roadster was supposed to use a two-speed transmission, but a fixed reduction-gear setup was substituted in after the unit wasn’t lasting in development cars, as it wasn’t able to handle the electric motor’s tremendous torque output.
Porsche says that it developed the gearbox for the Taycan on its own, internally. But perhaps in a vote of confidence for the market, suppliers are rolling out designs engineered for electric motors. ZF is bringing back its own clutchless 2-speed transmission for EVs earlier this year, and it notes that its unit could deliver a higher top speed and a five-percent improvement in highway efficiency.
ZF Friedrichshafen 2-speed EV transmission
Eaton also has an established 2-speed for commercial applications, and others are under development for passenger cars. It may also prove to be the enabler for electric SUVs and pickups to be able to combine towing and efficient cruising the rest of the time.
If there’s one glaring insight we see in the way Porsche has implemented the 2-speed in the Taycan, it’s that it doesn’t allow the driver to control shifts. Just knowing the 2-speed is there is going to be cause for some to want to control—but perhaps that chance to #giveashift will come in the aftermarket.
Fixed-ratio gearboxes should provide plenty of sweet spot for most electric vehicles for the near future, and the added weight of the gearbox might better be used toward more battery cells. But in premium and high-speed models, allowing taller drive ratios for high speed, without taking away from the perkiness at low speed, multi-speed transmissions might not be a thing of the past after all.