For most of us, the workings of an automatic transmission (or standard automatic transmission)remains one of life’s great mysteries. You pop the shifter from P to D, and magically the car instantly begins to lumber off. For a long time automatics were just garden-variety multi-gear units, so at least it was easy enough to know what to expect when you went out shopping for an automatic-equipped car, truck, or SUV.
That’s not the case anymore. In the last 10-15 years or so engineers have devised a number of different transmission types that all automate the shifting process but aren’t, technically speaking, automatics. The most prevalent of these is the continuously variable transmission, or CVT.
The CVT transmission is, on paper, the perfect solution to meet the often-conflicting requirements of performance, fuel efficiency, and smoothness. Yet enthusiasts love to rag on this transmission, and automotive journalists seem to hold a grudge against this hapless gearbox design. So what is it, and why has become such a polarizing bit of modern engineering? Does the CVT deserve the hate it gets, or is it all overblown?
Before we answer these questions, let’s first take a step back and consider the workings of the conventional automatic gearbox, and why we need gearboxes in the first place:
Automatic Transmission: What It Is (and Why We Need It)First developed by General Motors in the late 1930s, the fully automatic transmission made driving significantly easier and smoother by eliminating the need to manually shift gears (though the manual transmission has nonetheless remained available, even to this day). But why do we even need gears in the first place?
The best analogy is a bicycle. Imagine putting a 21-speed bike in top gear - gear three up front and gear seven out back. Now try starting off from a full stop. Difficult, right? It takes a lot of energy to turn those pedals one full revolution, and getting up to your top pedaling speed takes a long time.
Now imagine shifting down the lowest gear ratio: gear one up front and gear one out back. Now starting off from a stop is easy - you practically fly out of the gates like a jockey on a thoroughbred. But if you don’t shift, you’ll max out your speed very quickly. When that happens you’ll find yourself furiously pedaling without gaining additional speed.
The reason a single gear doesn’t cut it is because of what’s called a power band. The power band is that range of engine speed where the power is most smoothly, efficiently, and effectively being produced. You can feel it when a car when it kicks you back into your seat during hard acceleration. In this situation, the car is working in the heart of its power band and is being very effective at putting the power to the ground. It’s effective at putting this power to the ground because of proper gearing.
By having multiple gears of different sizes, you can always be in this powerband no matter what speed you’re going. Low gears keep you in the powerband when starting off from a stop; high gears do the same at high speeds. If a gasoline engine had only one gear, it would be like our bicycle analogy - you would either be very slow to accelerate from a stop but have excellent cruising speed, or you would sprint from a stop but be unable to reach high speeds.
An automatic transmission shifts among a set number of gears automatically. No manual input is needed from the driver. Sensors and computers determine when a different gear should be selected. In this manner the car automatically gauges and responds to a driver’s inputs and driving conditions, always striving for the best combination of effectiveness, smoothness, and efficiency.
Easy to operate and predictable in its operation, the automatic transmission has long satisfied consumers. Its very predictability has since become a metric of all transmission performance - which is precisely why the CVT has ruffled feathers ever since it first made its way into a production car.
What is a Continuously Variable Transmission? (CVT)Long the bane of enthusiasts, the continuously variable transmission is exactly that - a transmission that is constantly varying the gear ratio for the conditions at hand. How is this possible? By not using gears at all.
How it does what it does is actually quite simple in concept: two conical-shaped pulleys are connected by a belt. The pulleys can each become wider or narrower; as they adjust, the distance the belt travels changes. As it changes, so does the ratio at which the power from the engine is transferred to the driven wheels. The changing pulley size, and the resulting change in total belt travel, is like a constantly changing gear ratio. This is how a CVT is like having infinite gears.
In theory, having an infinite amount of gear ratios will always put you in the perfect ratio for the conditions at hand. Hard acceleration? There’s a ratio for that. Hypermiling? There’s a ratio for that, too. Trying to run a road course? There’s a ratio for every corner and every straight.
The problem that hobbles the CVT is that its behavior to accomplish this lies at direct odds with what our guts tell us is the proper behavior of an automatic transmission. With over one hundred years of having a set number of gears in our transmissions, we’re used to what’s called ‘stepped’ gears - the sense of our car ‘stepping up’ into a higher gear or ‘dropping’ into a lower gear.
The CVT doesn’t ordinarily operate like that. It’s instead in constant flux, adjusting to where it needs to be. In real life, this constant adjustment and lack of definitive shift points is unfamiliar and unnerving. And achieving maximum efficiency or power requires holding a set RPM for a prolonged period of time, resulting in irritating droning. It’s a lot less pleasing than hearing an automatic transmission snap off a quick shift when you floor the gas pedal.
Pros and Cons of CVTs and AutomaticsIn a traditional automatic transmission, one of the drawbacks is the set number of gears. By having only, say, eight forward gears, the powertrain is forced to choose one of those eight cogs for every situation. There are no exceptions to this. These are the only gears - and therefore only gear ratios - for the car to work with.
Ordinarily, this is rarely an issue. But for efficiency’s sake, a set amount of ratios limits the chances to reduce fuel consumption. This is solved with the CVT, thanks to its infinite ratios. The pulley system can constantly adjust so to provide the perfect ratio for any given situation, thereby maximizing fuel economy. This is the biggest benefit of the CVT.
Better MPG is not the only benefit of the CVT, either. Compared to a non-CVT, it’s lighter weight, has less moving parts - making it less complex, and can be more efficiently packaged than a typical automatic to provide better gas efficiency. It’s partly why its been used as a snowmobile transmission for years.
But the drawback with the CVT is its behavior as it constantly adjusts itself. Because there’s no sensation of a shift, it doesn’t feel natural. It also often holds the engine at higher RPMs, as there’s no higher gear to shift to. The result is a droning sound from the vehicle’s engine that isn’t exactly musical in its quality.
To compensate for this automakers have tuned CVTs to behave as traditional transmissions do, imitating both upshifts and downshifts in most conditions. This makes it feel more familiar to consumers but hurts efficiency, which ultimately takes away from the whole point of using this transmission in the first place.
Reliability has also been a concern with the CVT, and is another reason shoppers prefer the familiarity of the conventional automatic transmission. For instance, Subarus and Nissans of a certain age have been known to have CVT troubles. In most of these cases, a simple transmission service is difficult or impossible; service technicians will often recommended to replace the entire CVT unit - which can be thousands of dollars - or just buy a new car. Neither option is one that owners want to hear.
Common automatics don’t suffer these sort of drawbacks. Reliability varies from manufacturer to manufacturer, but for the most part they’ll last the life of the car. If they do act up, they can usually be fixed by specialists, and sometimes the remedy is as simple as changing the transmission fluid; if replacement is deemed necessary, a normal automatic transmission is also cheaper to buy than a CVT.
Cars With CVTBoth CVTs and automatic transmissions have valid reasons for existence, which is why plenty of automakers have fallen into either camp. Here’s a quick overview of some of the brands that have embraced CVTs with particular earnestness:
Honda: Many of the latest Honda products use CVTs. However, certain models continue to use automatics as well. For instance, Accords with the 2.0-liter turbo engine have 10-speed automatics, while 1.5-liter models use CVTs. Honda has tuned their CVT to behave more like a traditional automatic, so don’t write off the 1.5-liter motor found in the Accord and CR-V even if you’re adamantly against the CVT.
Subaru: The very first production car to ever use a CVT was the 1989 Subaru Justy. After a near-twenty-year hiatus Subaru began using a CVT again in 2010; now all Subarus but the BRZ sports car use it. There’s been some known issues with early CVT models that necessitated a recall of 1.5 million cars, but later models are supposed to have an improved design; to prove it, Subaru now offers a lifetime warranty for the CVT. We’d nonetheless recommend doing your homework before buying a used CVT-equipped Subaru.
Nissan: Another brand that began using the CVT in earnest in the early 2010s and suffered reliability issues; some owners have reported multiple transmission replacements in cars that haven’t yet seen six-figure mileage. Based on the internet, the problem is bad enough that visit any Nissan dealership and you’re bound to see the service department working on at least one CVT car. To remedy this Nissan has extended the warranty coverage pertaining certain years where the transmissions were particularly bad. The problems with Nissan CVTs are well documented, so do your research if you’re planning on buying a used CVT-equipped Nissan.
Toyota: Toyota uses a launch gear, which acts like the first gear in a regular automatic transmission. It works as a CVT as the vehicle kicks into higher gears. These fixed gear ratios increase efficiency and drive quality.
The Bottom LineLet’s be honest: change is hard. We’re creatures of habit, and anything not familiar we cast a wary eye on. The CVT’s much-maligned reputation is a victim of both our distaste for change and the teething issues that dogged early adopters of the technology.
Newer CVT vehicles promise better behavior, more reliability, and a heightened connection with the road. There’s also plenty of benefits with this type of transmission: a more compact design, better gas economy, and lighter overall weight.
If you’re going car shopping, don’t immediately write off all CVTs. Instead, do research, take a test drive or two, and decide if this technology is right for you. Plenty of good cars are equipped with CVTs, and there’s no reason to dismiss them from your short list for that reason alone.
If you’re ready to begin your own car buying process, you can search over 4 million new and used cars with iSeeCars’ award-winning car search engine that helps shoppers find the best car deals by providing key insights and valuable resources, like the iSeeCars VIN check report. You can search by a number of filters, including transmission type.