Efficiency and torque gains are the driving factors behind the new development.
This past week at the Electric Mobility Summit 2022 in New Delhi, a representative of the ZF Group made the point that a three-speed transmission could be a good fit for electric vehicles in the future.
If you don't know, ZF is a research and manufacturing powerhouse in the automotive, rail, marine, and industrial industries. In automotive circles, it's most commonly known as the supplier of the exceptional ZF eight-speed automatic transmission used in every front-engined, longitudinal vehicle from the BMW 3 Series to the Audi A8 and dozens in between. Even the retro off-roading Ineos Grenadier will use ZF transmissions. So when someone like V Ramanathan, head of OE business at the commercial vehicle division of the company, claims that electric vehicles could benefit from using more multi-geared transmissions, they probably have a point.
Ramanathan argued that using a three-speed transmission would make sense for efficiency. He mentioned that perhaps the lowest gear would be used for towing and difficult grades, the next for everyday driving, and the final ratio for high-speed driving. Amazingly, he also mentioned that ZF currently produces an axle-mounted three-speed transmission that would be perfect for these applications, praising its ability to offer high wheel torque and better range depending on the application.
Now, if you've been paying attention to electric cars in the past ten years, you probably know that most that have been announced or are already on sale don't use anything besides a single-speed direct drive transmission. It makes sense since electric motors don't need gears because they can make peak torque at zero RPM and still safely perform up to tens of thousands of RPMs.
When Audi and Porsche introduced the e-tron GT and Taycan, they announced that the EVs would use a specially designed two-speed transmission on the rear axle. The first gear would be used most of the time, then the second would come in at much higher speeds to help with efficiency. They did this because although electric motors are relatively efficient with a single gear most of the time, once you start to push high engine speeds for an extended period, you will notice your range drop drastically.
This development seems logical, but it appears we're just stuck in a cycle of repetition with automotive development.
When combustion engines were in vogue, we started with three-speed gearboxes, which then evolved to four-, five-, and six-speed variants. Once the human at the helm was no longer responsible for shifting, automatic transmissions grew to include as many as 10 forward ratios, something we can see becoming a reality with EVs at this current rate.
This may have just been a moment where a company exec tries to plug one of the company's new products, but he isn't wrong that there is a good case for it. Companies will take different avenues to address the problem, and it's best not to bite off more than one can chew. ZF has a lot on its own plate at the moment, as it will invest $14 billion into autonomous vehicle technology over the next five years as it breaks into a whole new production business.