What is a CVT transmission?

Many modern hybrid-engined cars use CVT gearboxes, but what is it and how do you use it? We explain it all…

A CVT (continuously variable transmission) gearbox is a clever form of gearbox that’s designed to make your car’s engine work in the most efficient way possible. How does it all work, though? Well, let us explain…

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What is a CVT transmission?

A CVT gearbox is unlike a conventional automatic gearbox because it doesn’t use six or seven different-sized cogs, or ‘steps’, when the car changes gear. Instead, a CVT uses a belt and conical-shaped gears, so shifts are smoother and stepless.

It’s a strange, but simple, concept. The belt is an elastic drive band that continuously varies the ratio between engine and wheel speed, ensuring that it stays permanently in the correct power band.

The idea behind the CVT has been around for centuries, with Leonardo DaVinci credited with designing the first CVT in 1490, and patents filed as far back as the 1880s (by a couple of chaps called by Daimler and Benz).

The first production car to use it, however, was the 1958 DAF 600, built in The Netherlands. A quirk of the DAF system was that the cars it was fitted in didn’t have a reverse gear: instead, the CVT box simply worked in reverse, which meant that theoretically, the cars had a top speed that was achievable going both backwards and forwards.

Since then, it has been traditionally applied in small-engined little cars, but its popularity, especially in Japan, means that manufacturers worked out how to use the system in larger, more powerful vehicles.

That means you’ll often find a CVT in Toyota and Lexus models, especially hybrid models, and cars from Honda and Nissan. South Korean manufacturers Hyundai and Kia also used to fit CVT gearboxes in many of its automatic models, but they have increasingly switched to dual-clutch transmissions (DCT) in recent years. The Multitronic gearbox in Audi models is a version of a CVT box too.

However, with 87% mechanical efficiency, CVTs are not the most efficient technology on the market. With stricter emission legislation and more efficient transmissions, such as DCT, now on the market, the days of the CVT may be numbered.

How does a CVT transmission work?

A CVT gearbox has a straightforward arrangement of two conical pulleys, with a V-shaped drive belt connecting them. One of the pulleys is connected to the engine, with the other connected to the wheels. When you press the accelerator, the engine turns over faster and the connected cone moves accordingly. The other cone adjusts to how the engine cone is responding to the amount of engine power, the drive belt maintaining the same tension. This determines how the car accelerates.

As the two cones move independently, there are no set gear ratios, essentially making a CVT a single-speed unit with an infinite number of gear ratios available. Its operation also explains why cars fitted with a CVT have a high-revving character, because the engine revs aren’t directly related to wheel speed.

The latest CVT-equipped cars have lots of soundproofing to ensure improved refinement and the technology has progressed so that the modern CVT gearbox is better than it used to be, both in terms of driving enjoyment and efficiency.

Indeed, Nissan has developed a CVT gearbox called Xtronic which features a number of ‘steps’ in its power delivery, which is designed to make it feel more like a conventional gearbox by ‘shifting’ through the gears.

Elsewhere, Toyota’s Hybrid Synergy Drive (HSD), which is used in hybrid models such as the Prius, uses a form of CVT gearbox as part of the hybrid system. This has a split power delivery so that the car’s engine is either driving the wheels or sending power to the battery.

Pros and cons of CVT transmission

Pros of CVT transmission

• Better fuel economy: A CVT transmission is designed to be the most efficient form of gearbox you can have, so you will get better fuel economy than if you use a traditional manual or stepped automatic gearbox.
• Smoother: With no gears to change, a CVT can simply adjust its transmission speed as needed, so there are no jolts or vibrations as the gearbox moves its mechanical parts around. A CVT is essentially always in gear, and always in the right gear.
• Better for hills: A CVT always keeps the engine in the right rev-range for the power you need, so it’s actually better for going up steep hills, as there’s no need to change down to a lower gear; you’re already in it.
• Easier around town: With no clutch to worry about, and no slack to take up in an automatic gearbox’s torque converter, a CVT is much more responsive and easier to use in stop-start town traffic.

Cons of CVT transmission

• Reliability: Generally, a CVT transmission won’t last as long as a conventional manual or automatic gearbox, and it’s more expensive to fix if it goes wrong. Just as well that most of them are made by Toyota or Honda, then…
• Power limit: CVTs aren’t designed for high engine outputs, so they’re no good for sporting or high-performance cars.
• Lack of involvement: Although there are CVTs with ‘fake’ gear changes designed into their software, essentially you can’t change gear in a CVT, so it’s less entertaining for a keen driver.
• Noise: A CVT’s mission is to keep the engine at the right revolutions for the performance you want, but that can often mean that a CVT will allow an engine to rev high and long, which can be annoying when compared to a conventional automatic, which will shift up to allow the engine’s torque to do the work. More recent CVTs have had improved software which reduces this problem, but it’s still an issue.

Which car manufacturer has the best CVT transmission?

As mentioned above, CVTs tend to be very popular with Japanese car makers, and for the most part it’s in cars from Japan that you’ll find the best CVTs. Toyota, which was one of the first companies to really embrace CVTs, generally makes the best, and has the most experience of making them. The CVTs in its current hybrid lineup are good enough that you mostly wouldn’t notice the change, if you swapped out of a conventional automatic gearbox and into CVT-equipped hybrid.

Lexus – Toyota’s luxury brand – also developed a remarkable CVT for the LC sports car, which used four physical gears backed up by an electric motor which could effectively turn those four gears into many gears, and which made for an especially effective gearbox with a bit more driver involvement.

Honda has also made many very impressive CVT transmissions, not least in the current Civic and CR-V hybrids, while Renault has taken a leaf from Lexus’ book and designed a CVT with four physical gears, no clutch, and not one but two electric motors which effectively gives it infinite gears. It’s used in the likes of the Clio, Captur, and Austral hybrids and is a little odd to use at times, but very effective.

Subaru makes some decent CVTs too, but probably the best CVT ever was one designed by the Williams Formula One team for its incredibly fast 1993 FW15C racing car, powered by a 790hp Renault V10 racing engine. Apparently it made the car even faster around the track, because the engine was kept constantly at its peak power output, but the CVT was only used in testing, and then the technology was banned by Formula One’s technical chiefs anyway.

What CVT problems to look out for

If you have a car with a CVT gearbox, it’s worth monitoring its performance, especially if the mileage is close to six figures. There are a number of tell-tale signs that the CVT in your car might not be running optimally:

• Slow shifting: You don’t have to shift a CVT from first to second gear, but you do have to shift between park, drive and reverse. If this change takes more than a second or so, you could have a faulty CVT.
• Strange sounds: CVTs are louder than their conventional counterparts, but humming and whining sounds aren’t normal. Excessive noise when accelerating is a tell-tale sign.
• Slipping: When accelerating, your car should experience continuous, seamless acceleration. If it slips or temporarily loses power, the CVT is faulty.
• Jerky shifting: When a CVT gearbox is shifting, it shouldn’t cause the vehicle to jerk.
• Inconsistent rpm: If you notice any fluctuation in the engine’s revs when driving at a constant speed, there could be a problem with the CVT.
• Dirty transmission fluid: When getting your car serviced, if the transmission fluid is dirty, this could indicate an issue with the CVT.

CVT transmissions FAQs

What does CVT stand for？

CVT stands for Continuously Variable Transmission, and it means a gearbox which uses cones and transmission belts, essentially meaning that it has one gear, but also infinite gears.

Are CVT gearboxes reliable?

Generally speaking, yes, although it helps that most CVT gearboxes are made by the likes of Toyota and Honda, two companies which tend to make very reliable cars. We’ve heard of some issues with the CVT box in the older Toyota C-HR model, so be aware of that, while Nissan had issues with its CVT too.

Are CVT gearboxes noisy?

No, in the case of a CVT, it’s not the gearbox that’s noisy – a CVT generally runs very quietly – but the way they’re designed to work means that for some power outputs, the engine is allowed to rev very high, for longer than you might expect, and so it’s the engine that can be noisy not the gearbox. Some CVTs can generate a slight whining noise, but for most this has been muffled by better sound-absorbing material.

Are CVT transmissions good for towing?

Not always. For larger models, most CVT models will have a comparable towing weight compared to a car with a conventional gearbox, but smaller cars – such as the Toyota Yaris Cross for example – will tend to have a lower towing weight than many rivals, around the 450kg mark. It’s also possible that towing a heavy weight up a long hill will increase wear and tear in both the CVT transmission itself, and your engine, because of the sustained torque requirement.

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