Skip to main content

What is a CVT Transmission?

CVT Transmission? How Does It work?

“CVT” stands for continuously variable transmission. A CVT transmission uses a pair of variable-diameter pulleys and a belt or chain to provide unlimited gear ratios.

How does a CVT work?

To illustrate, think of a traditional automatic or manual transmission. They’re built with a defined number of gears, for example first through sixth (plus reverse). The transmission can operate in only one gear at a time. You typically feel a slight surge with each gear change.

CVTs, however, offer unlimited gear ratios.

Take a look at the image. You can see the metal belt connecting the two pulleys. Depending on engine speed and load, the computer automatically varies the pulley sizes to ensure the optimal gear ratio for the driving conditions.

CVTs use variable-diameter pulleys to create unlimited gear ratios.

CVT transmission pros and cons

What good does that do?

Imagine pedaling a bike. As you approach a steep hill, you adjust the shifters so a smaller chainring attached to the pedals is driving a larger sprocket on the rear wheel. This reduces the effort required to move the bike.

When you reach a stretch of flat road, you adjust the gear ratio again so a larger chainring attached to the pedals is driving a smaller sprocket. This helps achieve the perfect balance between energy expended and bicycle speed.

The same principle applies to a CVT, except the computer does all the thinking for you. When starting from a dead stop, it varies the pulley diameters (smaller drive pulley and larger driven pulley) so the engine can move the car as efficiently as possible. As you accelerate, it continuously varies the pulley sizes to keep the engine in its “sweet spot,” which results in improved fuel economy. Plus, you never feel the gear engagements because, in effect, there aren’t any.

CVTs gaining in popularity – but there are negatives

These benefits are why many car makers, including Nissan, Honda and Toyota are introducing more vehicles with CVTs.

There are drawbacks, however, including the “rubber-band effect” (you rev the engine, yet it takes a moment for vehicle speed to catch up) and lack of driver involvement (zero fun). In addition, most CVTs’ relatively diminutive parts can’t handle the power and torque of the truck or SUV you use to tow your boat or camper, which is why you find them mostly on smaller cars. Although there are some exceptions, as the list shows, which shows popular vehicles with a CVT.

What cars have a CVT transmission?

  • Honda Accord
  • Honda HR-V
  • Mercedes-Benz A- and B-Class
  • Nissan Altima
  • Nissan Pathfinder
  • Subaru Forester
  • Subaru Impreza
  • Subaru Legacy
  • Subaru Outback
  • Toyota Camry
  • Toyota Highlander Hybrid
  • Toyota Prius

Slip into something special

One look at the guts of a CVT and you can’t help but wonder how the belt doesn’t just slip wildly over the pulleys.

Believe it or not, the transmission fluid plays a major role in ensuring the belt or chain remains in contact with the pulleys without slipping.

That’s why CVTs require specialized CVT transmissions fluids, and not the traditional automatic or manual transmission fluid you probably have in your garage. CVT transmission fluids must be formulated with the correct frictional requirements to guard against slipping. Using the wrong fluid will reduce performance and potentially wreck your transmission.

Wear protection also important

Solid wear protection is also vital to maximizing CVT performance and life. That’s why we designed AMSOIL Synthetic CVT Fluid to fight wear and help extend transmission life.

To demonstrate, we pitted AMSOIL Synthetic CVT Fluid against Nissan NS-2 CVT Fluid in a field trial. After 100,000 miles, the belt lubricated with AMSOIL Synthetic CVT Fluid demonstrated minimal wear, as you can see in the images. This helps you get the best performance and most life out of your CVT.

The belt lubricated with Nissan NS-2 CVT Fluid demonstrated increased wear.

Buy AMSOIL Synthetic CVT Fluid

While driving purists may initially scoff at the notion of a transmission that requires no driver input, many eventually warm up to CVTs’ increased gas mileage and smooth operability.

If you’re one of them, make sure you protect it with a good CVT transmission fluid.

Should I Change Fluid in a Filled-for-Life Transmission?

What’s up with these “Filled-for-Life Transmissions”?

Casual motorists generally take no interest in crawling under their vehicles on a Saturday afternoon. And, when was the last time you heard someone express excitement over dropping their car off at the dealership for maintenance?

The automakers know this, which explains the proliferation of sealed, or filled-for-life, transmissions and differentials. Many vehicles also use “lifetime” factory fill fluids in these components that supposedly don’t require changing. Some transmissions and differentials don’t even include dipsticks or access plugs for checking the fluids.

The dirty little secret is that “filled-for-life” really means “filled for the life of the warranty.”

Suppose the “filled-for-life” transmission or differential on your truck fails after the factory warranty has expired. What do you think the dealership is going to do? That’s right – slide a bill across the counter to the tune of several thousand dollars.

It’s a good idea to change fluids in a filled-for-life or sealed transmission or differential at least once during its lifetime, and more often if you tow or haul. Here’s why.

Big power = increased heat

Modern vehicles are tougher on transmission fluid and gear lube than ever. For starters, the automakers are in an endless arms race to produce more power than the competition. All that added power has to go through the transmission and differential before reaching the wheels, yet modern transmissions are smaller and lighter than their predecessors. Meanwhile, the gears and bearings in most differentials remain unchanged despite the increased power they must handle.

This adds up to increased heat, and heat is one of the transmission fluid’s biggest enemies. It speeds the oxidation process and causes the fluid to chemically break down. Fluid that has broken down can cause sludge and varnish to form, which clogs narrow oil passages and can lead to stuck valves. Soon, your vehicle can begin to shift hard, hesitate or quit shifting altogether.

The situation is just as dire downstream of the tranny where heat and pressure wreak havoc inside the differential. Towing and hauling increase friction, which in turn increases heat. Extreme heat causes the gear lube to thin, reducing the effectiveness with which it keeps gear teeth separated and prevents wear. Thinner gear lube further increases friction, which causes heat to increase in a vicious cycle known as “thermal runaway.”

Lighter fluid, and less of it

Components also use lower-viscosity fluids to help boost fuel efficiency. That translates into thinner fluid protecting against intense heat and wear – not an easy task. In addition, many automakers use less gear lube than before to help reduce energy lost to friction and boost fuel economy.

Given such challenging conditions, what’s the best way to combat heat and stress to ensure your vehicle keeps running strong? Never change the fluids? Hardly.

“Filled-for-life” is misleading

In fact, your “lifetime” fluid may require changing if your driving habits full under the “severe” designation, which includes towing and hauling.

The differential in the 2016 Ford Super Duty 250, for example, is considered “filled for life.” However, the owner’s manual instructs you to change the fluid every 50,000 miles (80,467 km) in “severe” conditions and anytime the differential is submerged in water.

Did you hear that, anglers?

The 2017 Toyota Tundra likewise features a “filled-for-life” differential. But Toyota tells you to change fluid every 15,000 miles (24,140 km) if towing.

Complicating matters, some vehicles don’t even include a service schedule for changing transmission fluid. The Mazda CX-5 is one example. That doesn’t seem like a great idea if you plan to keep the vehicle past its factory warranty period.

For maximum life and best performance, change the “lifetime” fluid in your vehicle’s filled-for-life or sealed transmission or differential at least once, but more often if your driving conditions fall under the severe designation.

Changing fluid in these units may tax one’s mechanical aptitude, but it can be done. You likely need to visit the dealer or a mechanic since special tools can be required. Some manufacturers also prescribe complicated procedures spelled out in a service manual for changing fluids.

Anyone who has changed gear lube before – whether on a “filled-for-life” differential or traditional unit – knows the hassle involved: a tough-to-reach fill hole, gear lube spilled everywhere and bloody knuckles.

Find out how often to change gear lube here.

Our SEVERE GEAR easy-pack offers the perfect solution. Compared to rigid conical bottles that waste a quarter of the gear lube or more, our easy-pack offers the dexterity to maneuver around vehicle components and the flexibility to install nearly every drop of gear lube. It eases the process of changing gear lube, saving you time and hassle.

video
play-sharp-fill