What is a CVT Transmission & is it Any Good?
The continuously variable transmission, or CVT, is finding its way into more vehicles all the time. Knowing more about CVTs can help you make the right decision when you’re buying a vehicle, and when you need to service it.
What does CVT mean and why do so many new cars have it?
While it seems like a modern invention, Leonardo da Vinci sketched a rudimentary design of one for machinery in 1490. In 1958, a European car called the DAF used a CVT, and starting in the late 1980s, some Japanese automakers did also. Some drivers in North America first became acquainted with them in the Toyota Prius hybrid, or on a snowmobile.
The main advantage to a CVT is that it’s efficient and improves fuel consumption. These units are also lighter than an automatic transmission, and have smoother acceleration.
How does a CVT work?
The engine contains a crankshaft that spins thousands of times a minute, referred to as r.p.m. for revolutions per minute. This spinning motion eventually powers the wheels, but it has to be converted to match the driving speed.
Conventional transmissions do this with gears. They use lower gears for the power to accelerate, and then higher gears for cruising that reduce the engine’s r.p.m. for better fuel economy.
Each gear in a conventional transmission has a fixed ratio. As you speed up or slow down, an automatic transmission shifts between the gears as needed; or if it’s a manual, you have to shift them yourself. On acceleration, you’ll hear the engine rev up (if it has a tachometer, you’ll see the r.p.m. indicator rise). The revolutions momentarily drop as the transmission shifts into the next gear, and then the engine revs up again.
Instead of shifting through a fixed number of gear ratios, a CVT seamlessly and continuously varies the gear ratio – hence its name – depending on what’s needed as you’re driving, no matter how fast or slow you’re going.
The engine r.p.m. will rise as you press the throttle harder, but the transmission simply keeps up, rather than forcing the r.p.m. to rise, drop for a gear change, and then rise again.
Rather than a set of gears, most CVTs have two pulleys. One is connected to the engine, called the driving pulley; while the other sends power to the wheels, called the driven pulley. Each pulley has two cones that can move farther apart or closer together, which changes the pulley’s diameter.
The pulleys are connected by a chain belt that runs between them. As one pulley becomes larger or smaller, the belt stays tight, which makes the other cone correspondingly smaller or larger to offset it. This provides the correct ratio for getting the engine’s power to the wheels.
CVT versus conventional automatic transmission: what’s the difference?
From an operational standpoint, a CVT and a regular automatic transmission are the same: You put the gearshift in Drive and then just drive as you normally would. Of course, as with an automatic, a CVT has Park, Reverse, and Neutral as well.
When CVTs started to show up on more vehicles in the mid to late 2000s, they often had a “rubber-band” effect. They did their job, but it felt like someone stretching and releasing a rubber band. They could have a noisy drone, too.
But they have improved considerably, sometimes to the point where it’s hard to tell the difference. Some have pre-set “shift points” to feel more like a conventional transmission, even though they don’t actually shift, since most drivers are used to that.
And just as some automatic transmissions have a “manual mode,” where you can sequentially shift between gears using paddles on the steering wheel or by pushing the shift lever a notch, some CVTs let you do this between the faux shift points for a sportier feel.
Common CVT problems
Some early CVTs could be prone to issues, but overall, most today have similar reliability to an automatic transmission – although if something does go wrong, they may be pricier to repair. As with other vehicle components, they should get routine maintenance. Follow the schedule found in the owner’s manual.
Because they’re different from an automatic transmission, drivers who aren’t familiar with them might not be aware of what could be an issue. Some indications that a CVT needs to visit a repair shop include loud moaning or whining sounds; a momentary loss of power or jerking when accelerating; or if the CVT takes a while to shift between Park, Reverse and Drive.
So, is a CVT worth having?
While they are increasingly found on a number of mainstream vehicles, including most hybrids, CVTs aren’t designed for heavier-duty or higher-powered performance vehicles, such as pickup trucks or sports cars. It is possible to tow with a CVT-equipped vehicle, but only if it’s recommended by the manufacturer and you stay within the towing capacity weight limit. You’ll find all of that in your owner’s manual.
CVTs have benefits, including good fuel economy. Acceleration and driving are smoother, especially if you’re on hilly terrain, where a conventional automatic may switch back and forth between two gears – known as “gear hunting” – as it tries to match a gear to the engine’s r.p.m. CVTs can also make smaller, lower-powered engines feel peppier than an automatic might, making it more fun to drive.
You won’t get a choice of CVT or automatic, just one or the other. But before you turn up your nose at a vehicle with a CVT, give it a test-drive. If you only remember the rubbery-feeling old ones, you might be pleasantly surprised with the newer ones.