Pros and Cons of Continuously Variable Transmissions

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By |2020-01-02T17:35:56-05:00November 27, 2019 - 07:29AM|Technology|

A growing number of cars and sport utility vehicles now come with a continuously variable transmission (CVT) instead of a conventional automatic. CVTs have been used in passenger cars since 1989, but if you haven’t been car shopping in several years, a CVT may be new to you. Here’s a quick overview of the technology.

CVT

What Is a CVT?

A CVT is a type of automatic transmission that delivers seamless acceleration without interruption for gear shifts. Instead of fixed gears, it uses a pair of variable-width pulleys that are connected by a flexible belt.

CVT vs. a Conventional Automatic Transmission

The purpose of any transmission is connect the engine to the wheels and help the engine stay in its optimal rpm range as it powers the car. Lower gears are good for low speeds and steep hills; higher gears are good for higher speeds.

A conventional automatic transmission uses a set number of low, medium and high gear ratios to send the engine’s power to the wheels. A CVT has no gears at all; it uses two variable-width pulleys connected by a flexible belt. One pulley is also connected to the engine, while the other is connected to the wheels.

The key here is that the width of the pulleys changes according to how much power is needed. One gets larger as the other becomes smaller. Because the pulleys and belt aren’t fixed, they can offer an infinite number of gear ratios between the lowest and highest gears. That’s compared to a conventional automatic, which usually has just four to eight gear ratios between its lowest and highest gears. This allows a CVT to deliver strong and seamless acceleration.

(A second, less common, type of CVT uses a series of discs and rollers.)

Pros of Using a CVT

Automakers are using CVTs for several reasons. A CVT can get maximum power out of a small engine for quicker and more responsive acceleration. That’s why you’ll most often find CVTs used in vehicles with four-cylinder engines.

CVTs also eliminate abrupt downshifting when additional power is needed for passing. A CVT likewise operates smoothly while climbing hills. This avoids the “gear hunting” you’ll often feel with a conventional automatic transmission. And because a CVT is lighter in weight and delivers better power efficiency, it helps improve a vehicle’s fuel economy. That’s why many hybrid vehicles come with CVTs.

Cons of Using a CVT

Some drivers find the sensation of continuous acceleration without shift points to be unnerving. If you like sportier driving, the absence of fixed gears can make downshifting and upshifting feel less engaging.

Another common complaint is that a CVT tends to make a vehicle drone loudly during acceleration. That’s because it often forces the engine to run at high, constant rpm as the vehicle gets up to speed.

Are CVT Problems Common?

CVTs are not without mechanical problems, and as with conventional automatics, it can be expensive to repair or replace a CVT. Search the website www.carcomplaints.com and you’ll find a number of common issues with CVTs. These include overheating, slipping, jerking, shuddering and a sudden loss of acceleration. As with any transmission, there are some cases where a CVT has failed altogether. The CVT belt, in particular, can be subject to excessive wear and stretching. In some extreme cases, owners filed lawsuits against automakers because of poor and unreliable CVT performance.

Which Cars Have a CVT?

If you’re car shopping, it may be difficult to tell whether a vehicle is equipped with a CVT or a standard automatic transmission. Both types look the same, with a shift lever that includes Drive, Neutral and Park selections.

CVTs are most commonly used in Mitsubishi, Nissan and Subaru cars and sport utility vehicles. Honda and Toyota are now including them in a wider range of models as well. They’re still far more common among Japanese import brands than the domestics or European imports. Generally, a given model offers either a CVT or a conventional automatic. The Honda Accord is the rare vehicle that offers both types. But in this case either transmission is available only with a specific engine, so buyers still don’t have a choice in the matter.

Though there are no gears in a CVT, some allow manual “shifting.” Here, the belt-and-pulley system moves to preset points that simulate changing gears. This is accomplished either by moving the shift lever or clicking on steering wheel-mounted paddles. As an example, the CVT in the Subaru Ascent SUV comes with eight of these shift points.

In the latest twist on the technology, the CVT in the Toyota Corolla adds what’s called a “launch gear.” This is like first gear in a standard transmission. The launch gear handles the car’s acceleration at speeds up to 25 mph, after which the transmission switches over to the belt-and-pulley system. Toyota says having the launch gear enables stronger and smoother acceleration from a standing start.

Shopping Tools From Carfax

There are a number of ways to tell which type of transmission a given vehicle includes. You can find this information on an automaker’s website, a printed brochure or the window sticker if it’s a new vehicle. If you’re shopping for used cars, it may require added research. Fortunately, our Car Research and Used Car Listing sections provide full details on most models on the market.

If you have questions about this story, please contact us at Editors@carfax.com

About the Author:

Jim Gorzelany has been covering cars for more than 30 years, with 17 of those spent as automotive editor for Consumers Digest magazine. He specializes in the vehicle buying and ownership experiences, with a few car reviews thrown in for good measure. Jim’s work has been featured in print publications including Forbes, Chicago Magazine, Men’s Fitness, Executive Travel and Muscle & Fitness, as well as websites including Forbes.com and Carfax.com. His weekly “Wheel Deals” newspaper articles are syndicated by CTW Features. Jim holds a B.A. in Communication from Southern Illinois University and lives just outside of Chicago.