Types of automatic transmission: how they work, how they drive and what the badges mean

• Used cars with a combustion engine or hybrid drive use five main designs: the torque converter automatic, the dual-clutch gearbox, the CVT, the hybrid e-CVT and the automated manual. Electric cars usually have a single-speed reduction gear that never shifts.
• The badge in an ad tells you the type of gearbox. DSG, S tronic, DCT and EDC are dual-clutch gearboxes, EAT8 is a torque converter automatic, Xtronic is a CVT, and ASG, ETG, Dualogic and x-shift are automated manuals.
• The torque converter automatic is the smoothest when pulling away and creeping in traffic. The dual-clutch shifts fastest. The automated manual noticeably interrupts drive with every gear change.
• Toyota's hybrid e-CVT links the combustion engine and the electric motors through a planetary gearset. Unlike a conventional CVT, it has no belt-driven variator.

Two cars without a clutch pedal can behave completely differently when pulling away, parking or accelerating hard. The types of automatic transmission differ in their construction, in how they transmit the engine's power and in how they change the gear ratio. That's why you hear such contradictory stories about ‘automatics’: one driver praises the silky shifts, another complains about jerkiness in queues. Often they're talking about entirely different technology. The abbreviation in an ad tells you more about how a car will drive than a gear selector marked P, R, N and D.

Every automatic takes the clutch and gear selection off the driver's hands, but the mechanism varies. In hybrids and electric cars, the same job is often done by a transmission that doesn't switch between conventional gears at all.

The different kinds of automatic gearbox differ most when pulling away, parking and accelerating hard. At a steady motorway cruise, most of them feel much the same.

Torque converter automatic: fluid transmits the power when pulling away

A hydrodynamic torque converter transmits the engine's power through the flow of fluid between the impeller and the turbine. Between them, the stator multiplies torque when pulling away. Once the car is moving, a lock-up clutch connects the engine to the gearbox mechanically, so the losses in the fluid disappear. The gears are formed by planetary gearsets.

You'll find this design mainly in mid-size and executive cars, in SUVs and in cars used for towing. Typical examples are the BMW 3 Series with Steptronic or the Peugeot 308 and 3008 with the EAT8 gearbox. Today's automatics have eight or more gears. A wide ratio spread, as in the eight-speed ZF 8HP, keeps the engine at suitable revs both when pulling away and on the motorway. The reputation of automatics as slow and thirsty comes from old four- and five-speed designs. This type is covered in detail in the article on the torque converter automatic.

Dual-clutch gearbox: the next gear is ready and waiting

A dual-clutch gearbox has two clutches. One serves the odd gears, the other the even ones. The mechatronic unit preselects the next gear, and the shift happens simply by handing drive over from one clutch to the other. Drive is barely interrupted.

The result is fast shifting and low fuel consumption. At very low speeds, however, the gearbox has to modulate drive with the clutch, so in a queue or when parking it responds differently from a torque converter automatic. There are versions with dry clutches and versions with wet, oil-cooled clutches.

You can't tell from the name or the number of gears whether a gearbox is dry or wet. The Škoda Octavia III (2012–2020) after its 2017 facelift shows this well. The 1.6 TDI 85 kW front-wheel-drive version had a seven-speed DSG with dry clutches. The Octavia Scout 2.0 TDI 110 kW also had a seven-speed DSG, but with wet clutches.

CVT: the ratio changes continuously

A CVT has no fixed gears. It changes the ratio by moving a belt or chain across a pair of conical pulleys, so the car gains speed without any gear changes.

In gentle driving, the CVT is the smoothest of all gearboxes and keeps the engine at economical revs. At full throttle, it quickly takes the engine up to high revs and holds them there while the car is still gathering speed. Some gearboxes soften this ‘rubber-band’ feel with simulated gear changes. The Xtronic in the Nissan Qashqai III (from 2021) with the more powerful version of the 1.3 DiG-T mild hybrid engine works this way, for example. Under hard acceleration, it mimics shifting between fixed gears.

Hybrid e-CVT: similar feel, different technology

In Toyota hybrids, the e-CVT label describes a transmission in which a planetary gearset links the combustion engine with two electric motors (motor-generators). The ratio changes through the way they work together. There's no belt and no pulley.

For the driver, the result is similar to a CVT: smooth drive without gear changes, and engine revs that don't rise in step with the car's speed when accelerating. One example is the Toyota C-HR I (2016–2023) in the 2.0 Hybrid version, which arrived with the facelift. Its transmission consists of two motor-generators, a planetary gearset and a reduction gear.

Automated manual: a manual gearbox shifted by actuators

An automated manual transmission, sometimes called a robotised gearbox, is a conventional manual gearbox. Electric or electro-hydraulic actuators operate the clutch and the gearshift for the driver.

With every gear change, it has to disengage the clutch, change gear and re-engage the clutch. The interruption in drive is therefore the price of the principle, and it causes the familiar head nod among the occupants. It was used mainly in small, inexpensive cars; newer generations have mostly replaced it with a dual-clutch or a torque converter automatic. Among used cars, you'll typically come across it in the Toyota Aygo II (2014–2022) with the 1.0 VVT-i engine and x-shift gearbox, or in the Volkswagen up! and Škoda Citigo badged ASG.

Electric cars: one fixed ratio is usually enough

An electric motor pulls from zero rpm and works across a wide rev range, which is why most electric cars need just one fixed ratio. The reduction gear lowers the motor speed to values suitable for the wheels and increases torque accordingly.

The Volkswagen ID.3 I (from 2019) with the APP310 drive unit creates its single fixed ratio with two reduction gear stages in series. So it never shifts. For reverse, the electric motor simply turns the other way.

Gearbox trade names help you get your bearings. Some denote a specific design; others are simply a brand's umbrella name for its automatics.

If an ad just says ‘automatic’, the exact type is determined by the technical data for that engine, year and drive layout, or by data looked up from the VIN. The make of the car and the number of gears aren't enough.

Parking and queues. The torque converter automatic is the smoothest here, because fluid transmits the power when pulling away. At low speed, the dual-clutch controls clutch slip, so it can feel less refined. The automated manual makes its shifts most noticeable.

Acceleration. The dual-clutch excels with its fast shifts. The CVT and e-CVT deliver a continuous pull, but accompanied by a long, high-pitched engine note. An electric car pulls without any delay at all.

Fuel consumption. The dual-clutch and modern automatics with eight or more gears are economical, the CVT keeps the engine at efficient revs and the e-CVT is part of a frugal hybrid drivetrain. It's mainly older automatics with few gears that use more fuel than a manual.

Towing. Thanks to its smooth starts and robustness, the torque converter automatic is best suited to towing. But the permitted trailer weight is always set for the specific version of the car, not by the gearbox badge.

The most common mistake is to apply experience with one gearbox to all the others. Even gearboxes of the same type differ between manufacturers and generations in clutch control, smoothness and maintenance.

• A name isn't an exact specification. The DSG badge covers versions with both dry and wet clutches, and Steptronic is just a trade name.
• Normal behaviour isn't a fault. The pause when an automated manual shifts or the steady high revs of a CVT are part of the design. Harsh jolts, vibration, slipping or warning messages, on the other hand, point to a problem.
• Simpler doesn't mean trouble-free. Besides the clutch, an automated manual has actuators that wear. A dual-clutch has two clutches and a mechatronic unit.
• Even an EV reduction gear contains fluid. Tesla, for example, describes the procedure for replacing the gearbox fluid in the rear drive unit of the Model 3 (2017–2023).

There's no single fluid change interval for all automatics; every gearbox has its own service schedule. The condition of the gearbox in a particular used car is revealed by its service history together with diagnostics and a test drive. Both diagnostics and a test drive are part of the CarAudit™ inspection that Carvago carries out on every car it sells.

Each type has its own article:

• DSG gearbox: how a dual-clutch transmission works and what to expect
• DSG: dry or wet clutch? The differences and how to identify the version in your car
• CVT gearbox: how it works and how the hybrid e-CVT differs
• Torque converter automatic: how it works and how it drives
• Automated manual transmission: how it works, why it interrupts drive and what to expect from a used one
• Do electric cars have a gearbox? How the reduction gear works and why it usually doesn't shift

Whether an automatic is worth having at all is covered in the article automatic or manual. How to drive an automatic, when to change the gearbox fluid and what to look out for in a used car are covered in the articles how to drive an automatic, automatic transmission fluid change and buying a used automatic car.

Once you know which type of automatic you want, you still need to find a car in good condition. Carvago offers roughly a million used cars from sellers in several European countries. The selection in practically every segment is therefore larger, usually by an order of magnitude, than on the local market, and that includes cars with a specific gearbox, such as a torque converter automatic in a compact car or a dual-clutch paired with a particular engine.

Every car is inspected by a technician before sale as part of the CarAudit™ inspection with up to 270 checkpoints. The inspection covers the technical components, diagnostics and a test drive, so it also picks up gearbox behaviour that you might miss on a short drive. You know the result before you decide to buy. Carvago stands behind the condition of the car stated in the CarAudit™ certificate and adds a free extended warranty to every car.

Before the sale, Carvago buys the car from the original seller, becomes its owner and takes on its risks. So you buy directly from Carvago, even if the car comes from another country.

Can I tell the gearbox design from the selector or the paddles behind the steering wheel?

No. All types of automatic use the P, R, N and D positions as well as paddles. On a CVT, the paddles switch between preset ratios, even though the gearbox has no fixed gears.

Does every hybrid have an e-CVT?

No. The word hybrid refers to a combination of combustion and electric drive, not to a specific gearbox. Hybrids from other brands also use dual-clutch gearboxes or torque converter automatics.

Are there electric cars with more than one gear?

Yes, but they're the exception. The Porsche Taycan I in Turbo and Turbo S versions has a two-speed gearbox on the rear axle. Ordinary electric cars make do with a single fixed ratio.

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