CVT vs Automatic Transmission: What’s the Difference?

When it comes to transmissions, cars used to fall under two categories: manual and automatic. However, a third type of transmission is growing in popularity, creating a third option: the continuously variable transmission (CVT). The CVT is actually a type of automatic transmission, but the two have distinct differences. What are the differences between CVT and automatic transmissions, and is one type better than the other? We look at CVT vs. standard automatic transmissions to help you understand what you need to know.

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 shift location relative to each other, becoming wider or narrower as dictated by the vehicle’s computer; as they adjust, the distance the belt travels changes. As it changes, so does the ratio at which the engine power 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 number 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 downside to the CVT is that its behavior to accomplish this lies at direct odds with 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 gear 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 constant engine droning with minimal change in exhaust note. It’s a lot less pleasing than hearing an automatic transmission snap off a quick shift when you floor the gas pedal. 

The Standard 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 to the lowest gear ratio: gear one up front and gear one out back. Now starting off from a stop is easy, 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 powerband. The powerband is that range of engine speed where the power is most smoothly, efficiently, and effectively being produced. You can feel when your car kicks you back into your seat during hard acceleration. In this situation, the car is working in the heart of its powerband and is being very effective at putting the power to the ground. Proper gearing makes this possible.

By having multiple gears of different sizes, you can always be in this high 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 away from a stop but 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’s unusual power delivery has drawn criticism ever since it first made its way into a production car.

Pros and Cons of Automatic Vs CVT Transmissions

In 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.