CVT Transmissions: Everything You Should Know About CVTs

CVT Transmissions are the only ones that make gear shifting seem, well, seamless.  A CVT transmission allows you to accelerate continuously from a standing start without shifting breaks and without an interruption in traction. And they are the only transmission on the planet that can do this, which makes them rather special. 

If you are here, you are probably wondering how is that possible, how does a CVT transmission work, is a CVT transmission reliable and so on. You are in luck, we will cover that and many other topics in this article, stay with us!

What is a CVT transmission?

A CVT transmission is a continuously variable automatic transmission. The abbreviation CVT stands for “Continuous Variable Transmission”. A CVT transmission does not use gears like other types of automatic transmissions, instead, it uses two conical pulleys or discs that are connected by a belt or a chain. 

Compared to a standard automatic transmission there is no pre-defined number of gears, there are no gears which is why you do not feel the gear changes, nor do you lose traction and power in between gear shifts. By using this principle, the entire engine’s power gets used without any losses.

How does a CVT transmission work?

In principle, a CVT transmission consists of two shafts, on each of which two conical disks, the so-called variators, are slidably mounted. The tips of the variators are opposite of each other, resulting in a V-shaped cross-section between the variators. The primary or input shaft or pulley is connected to the engine via a clutch and the second or output shaft/pulley leads to the differential gear and later, the wheels. The power transmission between the two shafts takes place via a wide, multi-row chain or belt. The chain lies between the variators on both shafts without touching the shafts themselves. If you change the distance between the variators of a shaft, the “gear” changes. This means that you essentially have an infinite amount of gears for every slight change of the variators.

When you start from a standstill, the variators on the first pulley (the primary shaft which is connected to the engine) are pushed apart as far as possible. The chain or the belt is as close to the input shaft as possible. The variators on the second shaft, on the other hand, are as close as possible to each other. If you can imagine a small gear and a big gear, this is the exact result you get by variating the two pulley shafts; a gear reduction from a small to large gear. To accelerate, the distance between the variators is reduced on the first shaft and increased on the second shaft.

By continuously changing the ratio, the second shaft rotates faster without the first shaft having to rotate faster. The engine can always work in the optimal power range. Only when the maximum transmission ratio of the CVT transmission is reached does the engine speed increase in order to continue accelerating.

What are the benefits of having a CVT transmission?

Seamless “gear” changes

Probably the most important advantage of a CVT transmission is the stepless change of gears. This allows the engine to take advantage of all its output.

Improved fuel consumption

By not losing any engine power in between gear changes, no fuel goes to waste which improves overall fuel efficiency.

Smaller and lighter design

Compared to manual transmissions, standard automatic transmissions and double-clutch transmissions CVTs are smaller in size and lower in weight. Since a CVT transmission does not require any pairs of gears for each gear, it can be built in a smaller form factor and it is also significantly lighter. Because of these advantages, Mercedes has developed CVT transmissions specifically for the W169 series A-Class and the W245 B-Class series. Both the A and the B class did not offer enough space for a conventional torque converter automatic transmission.

No shift lock and gear hunting

A CVT transmission is never confused about the gear that it needs to choose. The ride is always smooth and precise. This eliminates the annoying gear hunting when the car decelerates or when you are going up a hill.

Better acceleration and lower environmental emissions

We already mentioned that there is no loss of power as the car accelerates. This also translates into better overall acceleration. With almost zero power loss, no fuel goes to waste which means that CO2 emissions are lowered as well. According to the transmission manufacturer LuK, the efficiency of CVT transmissions could be increased to 98% by means of a special chain design, but for now, around 2% of the power is still lost (which is still amazing).

What are the disadvantages of having a CVT transmission?

CVT transmissions are subject to higher wear than other transmissions. 

Due to the high contact pressure between the variators and the chain, both components are heavily loaded and wear out more quickly. Despite the high contact pressure, there is always a certain amount of slippage between the chain and the variators. 

CVT transmissions require more maintenance than other transmissions. 

As a rule, more frequent oil changes must be carried out according to the manufacturer’s instructions. 

Maximum torque that can be transmitted is limited

These gearboxes are not suitable for large diesel engines and powerful petrol engines with high torque outputs.

Unusual sound and feeling

The biggest disadvantage for many drivers, however, is the unusual noise level when accelerating. When a vehicle with a CVT transmission accelerates, the engine revs up and then remains at those RPMs while the vehicle accelerates. This does not correspond to the usual noise development with a manual transmission or a torque converter automatic transmission.

Who invented the CVT transmission? 

In theory, CVTs transmissions go back to about 1490. It is said that in this year, the great da Vinci sketched the first stepless continuously variable transmission. About 400 years later, in 1886 a first CVT-related patent was issued for the first toroidal CVT. A few decades later in 1935, Adiel Dodge received a U.S. patent for a toroidal CVT and four years later, in 1939 the standard automatic transmission, based on planetary gear sets was introduced. The standard hydraulic transmission went on to dominate the automatic transmission market for decades to come.  

The first vehicle equipped with a CVT transmission as standard was a car from the Dutch car manufacturer DAF. In 1958 the DAF 600 was presented for the first time with a CVT transmission called Variomatic. It is a small car with a 600cm3 and 22hp engine. In the successor models of the DAF 600, 2 CVT gearboxes were often installed in the small cars.

In addition, the variators on the Variomatic were not adjusted hydraulically, but with the help of vacuum units, similar to those used for brake boosters. In theory, it was possible to drive backward with a DAF just as fast as forwards. More than 800,000 DAF passenger cars with CVT transmissions were built up to 1975. This year Volvo took over the Dutch manufacturer. After that, other vehicles with variomatic CVT transmissions were sold under the Volvo brand.

The first modern-era CVT transmission, known as Multitronic, was introduced by Audi in 1999 in the A6 models and later also in the A4 models. Since there were always major mechanical and electronic problems with these transmissions, they have now been replaced by the modern S-Tronic dual-clutch transmission. In Europe today there are only a few vehicles that are equipped with a CVT transmission. These are mostly small cars or vehicles in the lower middle class. In contrast, every third vehicle registered in Japan drives with such an automatic transmission. In Japan, these transmissions are still very popular because they offer a high level of driving comfort in dense city traffic.

How do I know if my car has a CVT transmission?

You can easily determine whether your vehicle is equipped with a CVT transmission or another automatic transmission. If, under acceleration, the engine RPMs do not change over a wide speed range, but the car still gets faster, then your car probably has a CVT transmission. With a torque converter automatic transmission, on the other hand, smooth shifting processes are noticeable and also audible because of the changing engine speed. A modern double-clutch transmission accelerates practically without any interruption in traction, but a change in engine speed is clearly audible with every gear change. You can also always ask the seller of the car you are buying if it has a CVT transmission or consult the owners and maintenance manual.

subaru lineartronic CVT transmissions
Subaru’s Lineartronic CVT transmission.

Are CVT transmissions reliable?

The answer is yes, modern CVT transmissions are considered to be just as reliable as standard automatic transmissions. There have been catastrophic problems with some early CVT transmission but as time moved on, manufacturers eliminated nearly all the issues plaguing CVT transmissions.

We do however want to note that there still are big issues with CVT transmissions that are not properly maintained. Regular transmission oil/fluid changes are even more crucial in CVT transmission than they are in any other form of automatic transmission. With poor maintenance come big problems, so CVTs commonly get a bad reputation when in reality it is the owners’ fault for neglecting the strict maintenance plan.

Can a CVT transmission be rebuilt?

Yes, CVT transmissions can be rebuilt. Anyone saying that they cannot be rebuilt, which is a common thing, is simply wrong. However, certain CVT transmission manufacturers will limit the availability of parts needed to execute a repair. They only offer replacement parts to dealerships.

Let’s use the Audi’s Multitronic CVT gearbox for an example. The most common issues with the Multitronic include broken transmission control module connections (TCM), faulty TCM and broken output shaft. While all the problems with the TCM can be resolved, no one can replace a broken output shaft as Audi does not sell or offer it separately. This means that rebuilding the Multitronic is limited and in a case of a broken output shaft, you simply need a new gearbox (which is insanely expensive).

How to drive a car with a CVT transmission?

Driving a car with a CVT transmission is really easy once you get used to it. We will admit it is a bit different than driving a DSG transmission, but in general, it is just shifting into Drive and taking off. That said, here are a few things you should know:

Do not slam the throttle aggressively

Slamming down the gas pedal in a car with a CVT transmission does nothing but cause trouble. As you put your foot down on the accelerator aggressively, your car’s RPMs will skyrocket, and your transmission will try to catch up with the speed you are demanding. In the long term, doing this can even hurt your engine. You will also notice a significant drop in fuel efficiency as your car will constantly operate at high RPMs.

Apply the throttle progressively

If you want to go fast in a car with a CVT transmission, you have to do the opposite of a “kick down” on a standard automatic transmission. With a CVT transmission, it is all about taking it easy and gradually. Do you want to reach fast speeds in the shortest amount of time? Just ease onto the gas pedal and let the transmission take advantage of every bit of your engine’s power. This might be against your instincts, but it is the way to go in a CVT car.

Do not use the throttle to stay still on a hill

Using the gas pedal to stand still on an incline is a good way to quickly damage your CVT transmission. Constantly engaging the clutch will overheat and destroy your transmission in the shortest time possible. Don’t do it.

Do not “Neutral Launch” the CVT gearbox

If you want to be a “racer” do not do it with your 115hp CVT car, you are going to regret it. Certain drivers like to apply gas in neutral, then suddenly drop into Drive in order to “launch” the car. Doing this with a CVT transmission is a sure way to end up with hefty repair bills at the dealership.

Do not shift into Neutral when coming to a stop

When you come to a stoplight, just hold the brake pedal. Shifting into neutral does no good for the CVT transmission and holding the brake in Drive mode does no harm to the transmission. If you are used to shifting into neutral from your previous manual transmission car, forget that habit as soon as possible.

Do not coast in neutral

Going downhill should always be done in manual or drive mode. Coasting in neutral can only mean that at one point you will need to shift into drive. Shifting from neutral to drive should always be done at a complete standstill. Many people however decide to shift to drive while they are coasting around in neutral. Never be one of those people.

Try learning how to shift manually when going downhill or uphill

In our opinion limiting the “shifting” of a CVT transmission can be beneficial when driving up or down a hill, but mainly down a hill. Unless it is a really steep incline, you should let the transmission figure out the correct gear ratio for the incline. If the hill is really steep, you should shift into L (low gear) so the transmission does not constantly search for the right gear ratio and overheat. The same applies when going down a steep hill. On a slight decline, letting the transmission do its job is probably the best idea. On the other, when you descend from a steep hill, shifting into a low gear and controlling the transmission can protect both the transmission and the engine.

Plan your overtakes

Getting full power from your engine with a CVT transmission take a second. Before you start overtaking, gradually apply the throttle and as you feel the power really coming on, go ahead and start overtaking.

Do CVT transmissions need transmission fluid replacement?

Yes, CVT transmission, even those with a “lifelong” transmission fluid need regular transmission fluid replacement. Most of the issues on CVT transmission develop because owners of CVT vehicles neglect the maintenance schedule.

Transmission fluid or oil has a number of functions in a CVT transmission. It keeps all the moving parts lubricated which prevents mechanical wear and tear. It keeps the transmission cool and protected against oxidation. Old and worn-out transmission fluid loses its lubricating properties as its viscosity drops. This leads to a higher level of mechanical wear and overheating of the CVT transmission.

When to change the transmission fluid in a CVT transmission?

We recommend that you change your CVT transmission fluid every 25,000miles or 40,000 kilometers. We would stick to this shorter transmission fluid replacement as it showed that it can greatly extend the lifetime of your CVT gearbox. Some manufacturers, like Nissan, also recommend replacing the transmission fluid every 25,000 miles.

How to check CVT gearbox fluid without a dipstick?

Not many CVT transmissions come with a dipstick that allows you to inspect the transmission fluid level. In case you do not have a dipstick, you should only let your mechanic inspect the transmission fluid in your CVT gearbox. Most cars will light up a warning light if your transmission fluid is running low.

CVTs without a dipstick have a fill or a level plug, which you can unscrew and top up the transmission fluid if it is needed. The maximum fluid level is usually just below the plug opening. Again, you should only do this if you are qualified.

Do CVT gearboxes need oil changes?

Yes, all CVT gearboxes require regular transmission fluid or oil changes. Failing to do so might result in a complete CVT transmission failure.

Does CVT transmissions have gears?

No, a CVT transmission does not have traditional gears. It features conical pulleys which transport a belt or a chain that acts as a variable gear. Some CVT transmissions have pre-set points in this variable transmission construction which allows the driver to manually shift “gears”.

How long do CVT transmissions last?

There is no clear answer, it all depends on the model of the transmission, how it is driven and how it is maintained. You can expect that a CVT transmission will last at least 100,000 miles but we commonly see them pass enormous amounts of miles (260,000 miles), especially in vehicles like the Toyota Prius.

Conclusion

CVT transmissions in today’s age are nothing to be afraid of. If we are honest, we would not buy a CVT transmission 15 years ago. But if you ask them the same question today, I would have no problems with having a CVT transmission in a small, city car. I would still not choose one in a car with more power, because I believe CVT transmissions are still not ready to take on a lot of power, even if manufacturers beg to differ.

If you are buying a used vehicle with a CVT transmission, first learn which transmission it uses. Some, especially older CVT transmissions were prone to failure even with perfect maintenance records. After you do your research about the CVT transmission in the car you are buying, make sure that it has a full maintenance history. Only then should you buy a used car with a CVT transmission.

If you are buying a new car with a CVT transmission, make sure that you get an extended warranty on the transmission, just for peace of mind. But we truly do believe that there is nothing you should be afraid of when buying a new car with a CVT gearbox.