Though continually variable transmissions (CVTs) don’t require a driver to manually change gears, they’re still very different from traditional automatic transmissions. Understanding how CVTs operate, as well as their pros and cons, can help drivers decide if a CVT equipped vehicle is right for them.
What Are Continuously Variable Transmissions?
Traditional Automatic Transmission
Traditional automatic transmissions operate similarly to a manual transmission, with different gear ratios required depending on factors like speed or road conditions. While manual transmission vehicles require drivers to determine what gear ratio they need to be at, automatic transmissions use a hydraulic system that responds to pressure created by those same driving conditions to automatically determine the gear.
The number of gear ratios that a vehicle has access to is a set number, with those ratios pre-determined so that there are adequate, if not ideal, ratios available for most common driving situations. These gear ratios are referred to as “speeds.”
Continuously Variable Transmission
While the first Mustangs had a meager three speeds, modern vehicles are often offered with ten, which is impressive. No matter how you look at it, there are a finite number of gear ratios that you can fit into a vehicle, but continuously variable transmissions try to change that by offering a virtually infinite gear range by doing away with gears entirely.
Continuously Variable Transmissions use a system of pulleys or rollers instead of gears. One pulley connects to the engine, the other to the transmission, and they’re able to adjust as needed to stay in an optimal range. The tension acts in place of individual gearing, allowing the car to vary its gear ratios as needed.
Though this sounds like the ideal transmission, and for many it is, there are some downsides of CVTs, including a distinct feeling that many aren’t fond of.
CVT Transmission Benefits
Because CVTs can adjust their gear ratios instantaneously and have an infinite range, they tend to be the most fuel-efficient transmissions by a wide margin. It’s been estimated that the average sedan with a CVT can get roughly 38 miles per gallon. Almost every hybrid has a type of CVT transmission for this reason.
Because of the lack of gearing, it’s easier for CVT vehicles to find and maintain an ideal torque ratio as well. Subsequently, CVTs have an easier time taking off from a stoplight and an easier time climbing difficult terrain. The variable transmission allows them to find the ideal gear ratio and stay in that range for longer. If you’ve ever driven a nice big block V8 up a mountain and been passed by a tiny hatchback with an attitude, it may have been equipped with a CVT-style transmission.
Naturally, without any gear shifts, the overall feeling of riding in a vehicle with a continuously variable transmission is significantly smoother than it is driving in a vehicle with traditional gear shifts. There are no pauses or drops in power as acceleration occurs. This also makes CVT vehicles ideal for stop and go traffic, hence why it’s the commuter transmission of choice. While other vehicles struggle to start back up from a red light, the small and efficient CVTs are able to easily accelerate.
Doesn’t Feel the Same
Many purists love the feeling of changing gears. Even on an automatic transmission vehicle that has gears, you can feel the jolt from the car transitioning over to the next gear. This isn’t true for CVT vehicles which provide continuous acceleration. Not changing gears impacts both the feeling and the sound. Without fixed gears, some CVT transmissions can feel like they are "rubber-banding" from ratio to ratio.
The sound of a CVT transmission is often best described as a drone. Though there are plenty of CVT advocates out there, you won’t find many that advocate for the CVT based on sound. It sounds high-pitched and continues infinitely, like a vroo-with no -oom. If the computer decides to keep the gear ratio at a certain place, you can be stuck in one rev range for longer than you'd like. Fortunately, CVT transmissions do seem to have gotten much better about this over the years, and continue to improve.
Lack of Power
CVTs tend to be exclusively designed for not particularly powerful four-cylinder engines, and need to be specially designed in order to deal with a lot of horsepower or torque. Subsequently, it’s unusual to find a CVT on a performance vehicle of any motorsport.
Harder to Work On
Other than mechanics, not a lot of people will feel comfortable working on a CVT vehicle, and that’s largely by design. Because CVTs are more complicated, they’re not designed to be self-serviceable and subsequently, even basic maintenance often has to be done by a dealership or otherwise equipped auto shop.
Continuously variable transmissions tend to be more expensive to make, and auto manufacturers aren’t shy about pushing that cost onto the consumer. Very rarely do manufacturers offer the choice between a traditional automatic or a CVT automatic, so in some cases using a CVT just makes the cost of not being able to drive a manual transmission vehicle significantly higher.
Initially, there were also additional costs associated with operating a CVT vehicle since the pulley system was more likely to break. This has mostly resolved over time, but the fact of the matter is that when CVTs break they typically need to be replaced, not simply repaired. Replacing a CVT can run up to $5,000 easily. Usually, this is a cost that’s to be expected as a vehicle nears 100,000 miles, though some have had CVTs for double that with absolutely no problems.
CVT Performance Features
Though continually variable transmission vehicles aren’t traditionally associated with performance, some manufacturers are trying to change that, and with new improvements to the existing technology, it seems like there are fewer reasons to restrict CVTs to small and light commuters. More auto manufacturers are equipping their CVT vehicles with performance-oriented features to try to encourage people to enjoy the sensation of driving a CVT at least as much as a traditional automatic.
CVT Paddle Shifters
Vehicles that have CVTs can still have manu-matic features like paddle shifters. Essentially, the paddle shifters are set to stepped “gear ratios” so there can be the sensation of manually changing the gears. You do also get all the benefits of up or downshifting if you choose to use these. Though there is a learning curve, once you learn to use paddle shifters they can offer a lot more control to an automatic.
CVT Launch Gear
Even though CVTs don’t have gears by design, some clever engineers have started to insert what’s known as a “launch gear” into CVTs. This helps to take some of the tension and pressure off of the belt and should help the CVTs to last longer.
In 1993, the Williams Formula One team did something incredibly daring. They used a CVT in their racer. Though the traditional thought process has dictated that CVTs don’t belong in performance vehicles, they reasoned that having infinite gear ratios would allow the car to stay in its peak power band indefinitely. Their trick was using a strong band to handle the 850 horsepower the engine was throwing down. No one has replicated their experiment because of a new rule made the year after banning CVTs, but it does indicate that performance-oriented CVT transmissions are possible.
Obviously, intelligent design features like a launch gear can help to extend the life of your CVT vehicle, but that isn’t something the individual user can control. The typical CVT lasts over 100,000 miles. Like any other transmission though, making sure that it’s taken care of will help ensure that you get as much life out of your transmission as you can. These are a couple of things you can do to increase the lifespan of your vehicle’s CVT.
The first big thing that you should do is establish whether your vehicle’s CVT has a torque converter or a clutch. Torque converter CVTs are more common, but if you have a clutch CVT you’ll want to be careful doing things like inching up in traffic with it.
Shifting from Reverse to Drive
Some drivers are bad about throwing their vehicle into drive straight from reverse while it’s still backing up. This can be hard on the transmission and serves no practical purpose.
Changing Transmission Fluid
Your owner’s manual gives you great guidelines on when to change your transmission fluid, but if you find a forum with others who drive the same vehicle you’ll quickly discover that they’ve developed more fine-tuned systems. For example, some Nissan CVT drivers recommend changing the fluid as often as every 30,000 miles or using a transmission cooler.
Is a CVT Transmission Right for You?
Overall, CVTs have a litany of pros that make them uniquely suited for many drivers. Though they have some peculiarities and require adjustment, the same can be said for any transmission.
If you’re looking for a fuel-efficient commuter or spend a lot of time driving in stop and go city traffic, then a CVT is likely to be the perfect transmission for your needs. Though the occasional droning isn’t particularly pleasant, it’s easy to block out with some music, and 40 miles per gallon is nothing to sneeze at.
If, on the other hand, you really prefer to shift gears on your own or are looking for a top of the line performance engine, then a CVT is unlikely to be the right transmission choice for you and you’d likely be much happier either looking at traditional manual vehicles or else perhaps considering a dual-clutch transmission, another transmission style that’s close to being automatic but that functions uniquely.
Sources: Ford | Engineering Explained | US News Image Credit: CarFax | Transmission Repair | TreeHugger | Williams