When choosing a car, one of the most important choices is picking the type of transmission the vehicle will have. In the past, this meant choosing one of two types: a manual transmission, also call a “standard” or a “stick-shift,” or an automatic.
Times have changed.
Now, the choices have multiplied as new technology seeps into every corner of our cars. Add in electric vehicles and their specialized transmissions, and things can get downright complicated.
Before we wade in to what kind of transmission does what and how, here a quick overview of what a “transmission” actually does for readers who might not have grown up with Porsche and Ferrari posters on their walls.
The transmission in a car (or any motorized wheeled vehicle) is a system of gears that literally “transmits” the power generated by the engine to the wheels that drive the vehicle forward. Figuratively and often physically located between the engine and the wheels, it’s a sort of middleman in the process that makes a car move, and it’s a complicated piece of machinery. Usually.
Let’s start with the basics:
Manual Transmission: Also known as a “standard” transmission or “stick shift” as noted above. This type requires you to push down on a clutch pedal and then change gears by hand with a shifter (the “stick shift”) in the center of the car. Most modern cars with a manual transmission have five speeds but some now have six, not counting reverse. In the early days of automobiles, all cars had manual transmissions.
Overall, the design is fairly simple, efficient and it gives drivers very direct control over the car, something driving enthusiasts like. On the down side, it takes a hand off the steering wheel to operate and using one in stop-and-go traffic can be a mini-workout. It also takes skill and practice to proficiently master a manual transmission.
Automatic Transmission: Also known as an “Auto.” First developed in the 1920s and refined ever since, most cars sold today come with an automatic transmission. And it’s easy to see why: there’s really no beating the convenience. Just put it in Drive, put your foot on the gas and off you go while the transmission picks the right gear for you no matter what the situation. But automatic transmissions are extremely complicated (albeit proven) and can cost you some miles-per-gallon due to their extra weight and slightly increased inefficiency when compared to a manual.
In the past, most automatic transmissions had three gears (plus reverse) and if it had four gears, you had a real hot rod – or a luxury barge. Now, automatic transmissions have up to eight gears, either to placate performance drivers or to give cars optimal gearing for fuel efficiency – or both.
With those two types out of the way, let’s move on to some sub-genres and new technology:
The Automatic Transmission with Manual Controls: As computers continue their infiltration into every system in a car, the automatic transmission has been given new abilities. Like we mentioned before, modern automatics now have up to eight gears. For the best of both worlds, car makers have been giving drivers the option to control the transmission manually, using a special “shifting” position on the gear selector or by using two hand-operated “paddles” located behind the steering wheel. “Paddle shifters” are more common on sports cars but they are popping up in more vehicles.
Drivers have always been able to “control” an automatic to some extent by using the gear selector but that really wasn’t the intended use and shifting an old-school automatic by hand could lead to the transmission failing if done improperly (or even when done properly, but too often).
Now, computer controls have largely taken care of that shortcoming and as the “automatic-with-manual-control” type of transmission becomes more efficient, smarter and inexpensive, it could replace manual transmissions as a choice. But we’ll see.
The Continuously Variable Transmission or CVT: If you’ve ever ridden a small modern scooter, then you are familiar with a CVT, or Continuously Variable Transmission. It’s a very simple design but one that works well under most conditions. Essentially, a CVT is comprised of two pulleys connected by a belt. But these are special pulleys since they can change their size and thus change the “gearing” in the vehicle. There are no set number of “gears” in a CVT because it can choose the exact gear ratio along a “variable” continuum between it’s lowest and highest gear ratios. So it can easily creep around a parking lot or blast down the freeway.
Driving with a CVT is much like using an automatic except there are no “gear changes.” Instead, the engine just revs smoothly up and down. Mash down the throttle and the car’s engine will jump to a higher RPM and then just stay there while the car goes faster and faster as the two pulleys in the transmission change their sizes. It can take some getting used to, and because of the somewhat odd driving characteristics of a CVT, some carmakers offer it with paddle shifters that mimic an automatic/manual transmission.
The CVT has been showing up in more cars recently. The advantage is the simplicity of the system and it can also be quite efficient if you don’t have a lead foot. If you do like to drive fast or want a high-performance car, this is an option you might want to pass on as it’s not really designed for that kind of driving.
It would seem that a CVT would be ideal for most drivers but it has taken time to mature the technology – especially the strength of the belt inside the transmission – from what’s required in a little scooter to the huge loads it is under in in a large passenger vehicle. But technology marches on and the CVT is becoming more common. It may even be a good fit for electric vehicles.
The Dual-Clutch Transmission (DCT): Widely known as a DCT or PDK transmission (thanks to Porsche) and others who use it in high-end sports cars and race cars, the DCT transmission is like a high-tech mashup of an automatic, a manual transmission and a computer.
Like its name implies, the system uses two clutches to change gears. The transmission can be used in a fully automatic mode, with a computer determining gear shifts, or as a manual, with the driver using paddles or buttons to change gears as they see fit. Additionally, the computer controls and shift points can typically be adjusted by the driver or even the computer itself so the transmission shifts in accordance to your personal driving style, such as whether the car is being aggressively or you’re just going for a leisurely cruise.
A DCT transmission can change gears with lightning speed – usually in a fraction of a second – and do so very smoothly thanks to the computerized controls, which makes it great for race and high-performance cars. While DCT transmissions are typically found in very expensive sports cars, they can be made compact enough that Honda also lists it as an option on several motorcycles. Riders can use it like a full automatic, or instantly change gears with two buttons on a small pod on the left handlebar. No manual clutch lever (or pedal, in cars) is required.
A DCT can be fairly small, relatively light weight and still incorporate a large number of gears. Since the mechanism is computer-controlled, it’s nearly impossible to damage it with missed shifts, so with proper care, it should last a long time. If you think you might be taking your new car to a racetrack for some “track days” or to a high-performance driving school, see if a DCT is an option. It may cost extra, but it is also a very trick piece of gear.
Electric Vehicle Transmissions
Electric Vehicles, or EVs, place different demands on a transmission that gasoline and diesel engines do not and as such, they have their own types of transmissions or use modified versions of those found in gas-powered vehicles.
Single-Speed Transmission: A common transmission at the dawn of the automobile and motorcycle eras was the simple connection of the engine to the wheels either directly or nearly so using a “one-speed” or single-speed transmission. At the time, automobile and motorcycle pioneers were more obsessed with getting their engines to run right, the transmission was usually cobbled together in such a way as to just get the wheels turning at all. But as the engines evolved, transmissions also became more complex. They started with one gear (often a belt attached to a reduction gear and then one of the wheels), and after losing a few muddy races, more gears were added to increase speed. And so it goes today.
EVs are essentially at that same early point in development, but with the hindsight of over a century of transmission refinement to draw on. Due to the nature of an electric motor, which can supply enormous power (more than most gas engines) from essentially a standstill, very often more than one gear is not required. This keeps things very simple for the car makers and also for the drivers.
The current poster child for electric cars, the Tesla Model S, for all it’s high-tech wonderment, has just one gear. But if you’ve ever driven one, you’d understand from the neck-snapping acceleration at nearly any speed, that’s really all it needs.
Conversely, the makers of the Brammo Empulse R electric motorcycle opted to change development of their bike to include a six-speed manual transmission, as their research indicated that’s what potential buyers with experience on gas-powered bikes wanted. However, you can also ride the bike around town in just first or second gear and never even touch the clutch, so you also get the best of both worlds.
Other EV makers have experimented with multi-gear transmissions, some unsuccessfully, and no one is quite sure what the future holds due to the different nature of power delivery from an electric motor. But like in the early days of gas-powered cars, you can bet there is much innovation and experimentation to come.
Will a CVT be the perfect transmission for a purely electric car? Or a DCT? Just the one gear most use now? Or some mix of the current technologies? Only time, research and development will tell.
As new transmission technologies evolve, so will this article. Check back to get the latest updates. Leave a comment about your favorite type of transmission.