Continuously variable transmissions have been used for years in motorcycles and snowmobiles. As cars and engines became smaller, the Environmental Protection Agency (EPA) lowered vehicle emission thresholds, and the price of fuel skyrocketed, the lighter-weight, fuel-efficient CVT transmissions (CVT), which also helped lower tailpipe emissions, became popular with manufacturers during the 1980s.
Like its cousin, the automatic transmission (AT), CVT transmissions are fully automatic and share many of the same characteristics. However, CVTs use fewer moving parts, shift gears (and gear ratios) are completely different from an AT, and they have a unique responsiveness on acceleration and a distinctive feel while driving. As an ASE and General Motors Master Technician and AT expert for over 50 years, I’ve seen how CVT evolved and has become more durable and longer lasting. Ahead, Subaru and ASE Master Technicians and the owner of a CVT vehicle provide professional and firsthand expertise explaining how CVT transmissions work.
What Is CVT Transmission?
“Simply put,” says Eric Maldonado, a technician at Subaru of Cherry Hill, “an automatic CVT transmission uses a fixed length steel chair or ‘belt’ positioned between a pair of two movable, or adjustable, conical shaped pulleys to transmit engine power [from the drive pulley] to the driveshaft [through the driven pulley] and ultimately to the wheels.”
The belt sits higher or lower on the pulley surfaces of a CVT transmission, and as the pulleys move closer together or farther apart, in principle, they become variable diameter gears, providing an infinite number of gear ratios. “As the pulleys move, the belt seamlessly transfers power from one pulley to the other, enabling smooth acceleration,” adds Frank Romano, a technician at Subaru of Cherry Hill.
How Are CVT Transmissions Different?
CVT transmissions are simpler in design and function and have fewer moving parts than a traditional AT. Depending on the number of “speeds” an AT has, there can be up to four complex planetary gearsets and up to six friction clutch packs that provide up to 10 fixed ratio forward gears, plus reverse gear.
In an AT, pressurized automatic transmission fluid (ATF) is routed to clutch packs that lock and unlock the planetary gearsets. Transmission gear and gear ratios are fixed and determined by which parts of the gearsets are freewheeling or being held stationary by the clutch packs. Pressurized ATF acts on the movable half of the pulley, changing its diameter. “Consequently,” said Maldonado, “a CVT transmission continually changes gear ratios as the two movable pulley halves slide on a shaft, while the other half of the pulley remains locked in place.”
In other words, from a stop, the two halves of the drive pulley are close together, increasing the diameter of the drive “gear” while the two halves of driven pulley are further apart and thus a smaller diameter. This positioning proves the torque and power of “low gear” needed to accelerate from a standstill. The opposite takes place on acceleration until you reach “high gear,” and the space between the driven pulleys narrows as the space between the driven pulley widens.
Remember, since the length of the belt is fixed, “both movable pulleys must remain synchronized to maintain constant tension [on the belt],” said ASE technician Tom Diamond. “This [design] maintains belt tension to prevent the belt from slipping,” said Romano. The gear ratio is determined as the radius between the driven and drive pulleys changes. Since CVTs do not have fixed gear changes based on vehicle speed, engine speed and load, throttle position or other inputs, acceleration is smooth and continuous.
“You will quickly notice there’s no shift “bump” when the AT changes gears,” added Diamond. Greg Efie, Service Manager at Subaru of Cherry Hill explained, “many drivers actually complained about not feeling the transmission shift. This led to Subaru programming ‘fake shift points’ into the computer to add the sensation of gears changing.”
IMAGE: CVT-Illustration
How Are CVT Transmissions The Same As Traditional Automatic Transmissions?
“Both transmissions strive to deliver smooth and comfortable driving experiences, provide better fuel economy and lower emissions,” said Maldonado.
In addition to automatic shifting and being computer-controlled, traditional AT and CVT transmissions both use torque converters (a fluid coupling—a hydraulic counterpart to a manual transmission’s clutch) to transfer an engine’s rotational power to the transmission.
CVT also uses a single clutch pack and planetary gear set for reverse only. Although they both use transmission fluid, CTV fluid contains different and unique properties than standard ATF. Distinctive properties prevent the transmission from overheating by quickly dissipating heat produced by constant belt and pulley movement while improving and maintaining correct belt friction that reduces belt slippage, ensuring smooth operation and longer CVT life.
Does My Car Have CVT Transmission?
Most hybrids and plug-in hybrid (PHEV) vehicles come standard with CTV, but some cars may have a badge on the transmission dipstick (not all CVTs have dipsticks) or “have markings on the transmission itself,” said Romano.
The easiest way to check is to read the owner’s manual. Many newer models from Toyota, Nissan, Subaru, Hyundai, Honda and General Motors come equipped with CVT as standard equipment.
Benefits and Drawbacks of CVT Transmissions
Benefits:
- Provides maximum power for smaller four-cylinder cars.
- Increases fuel economy while lowering emissions.
- Offers smooth, continuous acceleration.
- Learns and adjusts to your driving habits.
Drawbacks:
- Lacks shift point “feel.”
- Fluid expensive.
- Noisier than traditional AT.
- Lower life expectancy and more mechanical issues and failures than traditional AT.
- Belt slippage and wear increase as high voltage hybrid and PHEV batteries weaken.
FAQ
How long do CVT transmissions last?
How long a CVT transmission lasts depends on various factors. Although the belts are designed to last the life of the transmission, Maldonado explained, “a traditional AT should last 200,000 miles, but many times CVT often fail and need replacing at 100,000 miles.”
Of course, Romano added, this all “depends on your personal driving habits, the climate where you live, and where you will be doing the majority of your driving.”
Performing regular maintenance and making repairs when needed will also extend the life of any car part. Diamond explained “the car will jerk or [the transmission] will slip on acceleration when a belt overheats.” Eife said he has 95,000 miles on his Subaru Outback and “has never experienced any transmission problems.” He also mentioned “Subaru extended the powertrain warranty of their cars to 100,000 miles” to show their earlier CVT transmission issues have been remedied and are now more dependable.
Do CVT transmissions need more maintenance?
According to Maldonado, whether a CVT transmission needs more maintenance depends on the manufacturer. Some CVTs come sealed and, under normal driving conditions, do not require any maintenance. He added, “If you live in climates where extreme hot or cold temperatures are normal, or drive in dusty dirty conditions, then changing CVT fluid should be done every 50,000.”
Other manufacturers recommend ATF exchanges every 60,000 miles. Other manufacturers recommend to periodically inspect the belt (if possible). As always, refer to your owner’s manual for specific maintenance schedules and recommendations. Maldonado said most CVT “come with a drain plug, and you can change [or flush] CVT fluid yourself. Just be sure to use the specified CVT fluid for your make, model and year,” he cautioned.
The Experts
- Eric Maldonado has been a Senior Subaru Master Technician and transmission expert for the past eight years at Subaru of Cherry Hill, located in Cherry Hill, NJ.
- Frank Roman has been a Senior Subaru Master Technician for 28 years at Subaru of Cherry Hill.
- Greg Eife, was my former apprentice, is an Oldsmobile Master Technician and now servers as Service and Parts Director of Subaru of Cherry Hill.
- Tom Diamond has over 30 years of experience in the automotive repair industry as a technician, certified original equipment manufacturer (Mazda) trainer and shop supervisor. He has been an ASE Master Technician for over 25 years, including ASE L1 advanced automotive engine performance certification and is a PA Department of Transportation certified state safety, emissions and reconstructed vehicle inspector as well as a certified welder. (Interview Feb 18, 2025)
Resources
- Dave Bodzioch has more than 20 years of experience as an ASE Master Technician is a Pennsylvania Department of Education certified Automotive Technology and Outdoor Power Equipment instructor at North Montco Technical Career Center in Lansdale, PA.
- Future Tech, Webinar: “Electrified Vehicle Inspections: What Sets Them Apart from Conventional Cars?”
- Armor Lubricants: “Transmission Fluid for CVT Transmission vs ATF! What is the difference?“
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