If you’ve been looking for a new car, you might have come across different types of automatic transmissions, including the traditional torque converter (commonly called automatic transmission) and the relatively new CVT (or continuously variable transmission). But given that both transmissions offer added convenience by changing the gears or engine’s output for you, what exactly is the difference between the two?
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At the core of every car is its engine, which converts the chemical energy of the fuel into mechanical energy that rotates the crankshaft. Then, the motion is transferred to the car’s transmission, which uses a combination of gears (with a manual or automatic gearbox) to pass on the momentum to the driveshaft and, finally, to the wheels.
While that’s a rather brief description of how a car’s powertrain works, it sets a context about the role of the transmission: to transfer power from the engine to the wheels. To achieve this, a transmission usually employs gears to adjust torque and speed.
Now, it’s either you engaging the clutch and changing the gears through the stick in the cabin, or it’s a set of computers and actuators doing the job for you, which is where CVT and automatic transmissions (AT) come into play. Both options provide a convenient driving experience. However, the way they work and the driving experience they provide is slightly different.
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How does a traditional automatic transmission work?
As the name suggests, automatic transmissions take care of the gear shifts on their own, without the manual intervention of the driver. Instead of an external clutch, cars with automatic transmissions use a series of internal clutches engaged by a computer-controlled hydraulic system. When you press the accelerator, the engine starts generating power, which is then transferred to the transmission through the torque converter unit.
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For those catching up, the torque converter consists of an impeller, a turbine, and a stator. These, along with the transmission fluid, ensure optimum power delivery to the transmission for better acceleration. Besides the torque converter unit, an automatic transmission also uses a planetary gear system, which consists of a central or sun gear, a set of planet gears, and an outer ring gear that surrounds the entire configuration.
Together, the transmission and the planetary gear system produce multiple gear ratios. As the driving conditions change (including the vehicle’s speed and the intensity of throttle or brake), the Transmission Control Module (TCM) determines the appropriate gear ratios and engages them with the help of a hydraulic system. Generally, the hydraulic system uses multiple clutches and brake bands to ensure timely shifts for maintaining performance.
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Instead of a complex gear system, CVT uses a belt and pulleys
A continuously variable transmission, or CVT, also allows you to drive without the hassle of manually changing gears, but it achieves the feat with a different approach. As the name suggests, a CVT uses infinite gear ratios to balance the power and the speed required by the car. And even though the concept of gear ratios applies to this type of transmission, it doesn’t rely on physical gears like a regular automatic transmission.
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In a vehicle with a CVT transmission, the power generated by the engine flows directly into a belt and pulley system (instead of a planetary gear system), which usually consists of a primary (or drive) pulley connected to the crankshaft, a secondary (or driven) pulley connected to the driveshaft, and a belt that connects them. Now, as you drive a CVT car, the TCM and hydraulics system keeps adjusting the diameter of the pulleys and the position of the belt that’s wrapped around them to control the power delivery.
Between varying speeds and engine load, each belt-and-pulley combination acts as a gear ratio in itself. This is how a CVT transmission offers an infinite range of gear ratios, allowing for a smooth and comfortable ride.
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Automatic transmissions offer better performance and are easier to maintain
The torque converter unit in an automatic transmission helps multiply the engine’s initial torque, resulting in a smooth takeoff. To optimize the performance in different driving conditions, manufacturers often include drive modes (like Comfort, Eco, Normal, Sport, etc.). An automatic transmission also offers rather timely shifts between gears with a proper sense of upshift or downshift, making the driving experience more engaging and, at the same time, familiar.
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While traditional automatic transmissions are known for their ease of use and reliability, they tend to consume more fuel than manual and CVT transmissions, especially in lower gears. To counter this, manufacturers often equip vehicles with more forward gears, so that the vehicle operates efficiently at higher speeds, which, in turn, increases the effective mileage.
Even though automatic transmissions are slightly more expensive than CVTs (due to the presence of more components), they are relatively easier and cheaper to repair or replace. If you ever face a breakdown, you’ll likely get help at the closest third-party auto repair shop. Coming to the downsides, automatics often have a characteristic shift lag, which is more noticeable under higher throttle inputs and at higher RPMs. Further, the system may struggle to find the right gear while climbing a steep incline.
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CVTs are tuned for a smooth driving experience and better fuel efficiency
When compared to an automatic transmission that offers a balance between power and fuel efficiency, CVTs are tuned to keep the engine running at its peak efficiency, offering better fuel economy. In addition, a CVT unit is lighter and smaller than a conventional automatic. That is why you see this type of transmission used in hybrid cars, as it is more fuel efficient than a manual or a traditional automatic transmission.
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A CVT unit doesn’t shift gears at all: the lack of physical gears makes it easier for the transmission to stay in the ideal gear ratio throughout the ride. This eliminates the shift lag or gear-hunting behavior we discussed earlier, resulting in a smoother, more comfortable ride. Hence, if you’re looking for a car for an elder in your family, CVT could be the right choice. However, this also takes the fun element out of the driving experience, especially for enthusiasts.
For the uninitiated, manufacturers have started including paddle shifters on certain models. They mimic predefined gear ratios and make a CVT transmission feel livelier and engaging. You’ll notice that CVTs are cheaper upfront, but what isn’t immediately apparent is that they have slightly higher upkeep demands, like more frequent fluid replacements and relatively expensive maintenance (which often requires specially trained technicians). Last but not least, CVT systems usually don’t last as long as automatic transmission.
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Automakers have shifted to CVTs for budget-friendly cars
Due to their lower upfront cost and higher fuel-efficiency figures, CVTs are becoming increasingly common in affordable cars like the Toyota Camry, Honda Civic, and the Hyundai Elantra. Other models that offer a CVT transmission include the Mitsubishi Mirage, Nissan Versa, and Chevrolet Trax. In fact, unless you’re looking for automatics specifically, there’s a good chance you might end up with a CVT. If you’re on the lookout for a pocket-friendly vehicle for your family’s daily driving, professional commute, or as a secondary car for your household (especially for someone older), CVT is definitely worth considering.
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Given their higher manufacturing cost, automatics aren’t available on as many vehicles as they used to be. It has become difficult to find a torque converter transmission, especially on a budget. However, a few models exist, such as the Hyundai Sonata, Toyota RAV4, and the Ford Mustang EcoBoost Fastback. While the first two have an eight-speed automatic gearbox, the last one has a 10-speed torque converter unit (with paddle shifters). Go with an automatic transmission if you’re an enthusiast, want better performance, and don’t want to miss the gear shifts while driving.
Even though you know how the transmissions work and what differences their driving experience entails, we’d suggest you take test-drives before putting your hard-earned money on a car.
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