Just over two years ago, I wrote an article discussing upcoming EV transmissions. Since then, we’ve seen a number of EVs and plugin hybrids that use a transmission, and the advantages that were mathematically predictable (as well as known from the DIY EV scene that predated mass EV production) became a reality.
Last month I had a chance to experience this for myself, and I wanted to share what I learned from the experience.
Why EVs Benefit from Transmissions
Before I get to my specific experience, I want to go over the reasons EV transmissions are a good thing.
Tesla fans tend to think that transmissions aren’t necessary or good because they think Tesla’s vehicles don’t have a transmission. If they’re doing okay without one, then it must not be important, right? If you look more closely at Tesla’s dual motor offerings, you’ll find that they have a transmission of sorts, and reap those benefits in a rather creative way.
Yes, it’s true that an electric motor can operate across a much wider range of speeds (RPMs) than a gas engine. To roll down the road, it’s not strictly necessary to have multiple gear ratios to avoid over-revving the electric motor the way you’d over-rev a gas or diesel engine. Eventually (often before 40 MPH), you need to shift to a higher gear to not destroy the engine. EVs can just stay in a single gear that covers all of the vehicle’s speeds, so you can do without a transmission.
The fact that an EV can do without multiple gear ratios doesn’t mean they can’t make things a little better, though, and Tesla knows this. At low speeds, a Tesla can send more power to the rear wheels where they’ll do better for launching. At higher cruising speeds (highway driving), the power gets diverted mostly to the front motor, which has a higher gear ratio, effectively giving the vehicle a second gear. Plus, the front motor on performance models is smaller and is better suited to this task.
Porsche took this idea to the next level by introducing a two-speed transmission in the rear drive unit. At highway speeds, both the front and rear drive units employ an 8.5:1 gear ratio, but the rear motor can go as high as 15:1, allowing for way more torque multiplication during the initial launch, before switching to a gear that’s taller than the Teslas for highway cruising.
This, along with other factors, explains why the Taycan got such a good number in Edmunds‘ range testing. In its most efficient drive mode (which the EPA doesn’t use), it got far more range on the real highway than anticipated, while the Tesla fell a little short of EPA estimates.
But what happens when we go beyond 2 gears? Would an EV benefit from 3, 4, or even 5 speeds? As we’re finding out, it turns out that the answer to that is “Yes.”
What I Learned From the Wrangler 4xe
Yes, I know, the Wrangler 4xe is a plugin hybrid. Before you all get the rope, I’m only going to be discussing the vehicle’s behavior in EV mode in this article. I won’t be discussing any hybrid behavior, gas engines, etc.
As I pointed out in this other article/video, upcoming full EV off-road vehicles are going to be awesome. The biggest advantage is going to be how controllable they are at low RPM. Instead of having to gas-brake-gas-brake over obstacles, you can give it just the right amount of power to smoothly climb an obstacle. This advantage is greatly magnified by gear reduction, so running in 4-Low in the vehicle’s lowest gear allows for not only amazing torque at the wheels, but a great amount of control over that torque.
The whole off-road experience is far smoother than internal combustion, but the vehicle surprised me in another way on the road. With the radio off, driving around town in two wheel drive, I noticed that the electric motor’s whine would slowly rise in pitch just like any EV. Just like my LEAF, most of the torque was down low, and the amount of acceleration power would taper off as the vehicle increased in speed.
The surprise came about the time torque was tapering off. The pitch of the electric motor dropped, and the torque suddenly came back for a second wind. After the torque dropped off again, it happened again. Instead of driving the electric motor in one gear, the Jeep was running it through the transmission and shifting, allowing for better torque at higher speeds, as well as better range than it would have achieved under just one gear.
I knew what I was feeling, but to confirm it, I did some menu diving and got the gauge cluster screen to show what gear it was in. Just as I had suspected, the car was shifting gears as it accelerated, and this was very good for the little electric motor’s performance.
More and Better Are Coming
As I pointed out earlier, this was just how the vehicle behaved in electric mode, and was just part of a larger drive system that involved an ICE. That doesn’t mean manufacturers aren’t planning on building full EVs with transmissions.
While various sources on the internet think we’ll eventually see a 3 or 4-speed automatic EV transmission, prototypes show us that there’s a lot more variety possible.
The wildest thing out there right now is Jeep’s Magneto concept. It’s a full EV (not a hybrid), but runs the power of its electric motor through a manual transmission. That may sound like an awful thing, but keep in mind that electric motors can’t stall. You can just leave the manual transmission in gear as you approach a stop sign or red light and come to a complete stop. Once you’re ready to go again, just step on the skinny pedal. Shifting would only be needed for getting on the highway or if you wanted to make a hard launch in first gear.
Building more EVs with transmissions could also help make the experience of driving one a lot more comfortable for people who have been skeptical of EVs thus far. By making it so they don’t have to give up what they are accustomed to, we can help get more people to switch.
For all of these reasons, EV transmissions are awesome, and we need to see more of them.
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