How does an automatic gearbox work? The different types explained

An automatic gearbox does the same job as a manual gearbox, but without you having to use a clutch or change gear yourself. Every gearbox adjusts the ratio between the engine and the wheels. Pulling away needs a lot of pulling power, while on the motorway you want low engine revs. The ratio between the gears decides how fast the wheels turn at a given engine speed.

In a manual gearbox you choose that ratio yourself with the clutch pedal and the gear lever. In an automatic, a control unit (a small computer) does it for you. It looks at things such as your speed and how far you press the accelerator. How the gearbox transmits power and changes ratio differs from one type of automatic to another. That difference also decides how the gearbox feels, which problems can occur and which maintenance it needs.

The fluid in the gearbox plays a big part in every type. According to the ANWB, the Dutch motoring organisation, gearbox oil lubricates, cools and keeps dirt away. In an automatic with a torque converter and in a wet DSG, the fluid also transmits power and operates the clutches inside the gearbox. That is why the condition of the fluid matters even more in those gearboxes.

There are four main types of automatic gearbox in passenger cars. The table puts them side by side. After that, you can read how each type works.

Sources: ANWB (gearbox explained) and BOVAG (buying a used car with an automatic gearbox).

According to the ANWB, hybrids from Toyota and Lexus, among others, also have a kind of CVT. It works with a planetary gear set and is technically different from a CVT with a push belt. You can read more about it further down.

A conventional automatic transmits the power of the engine through a torque converter. This is a fluid coupling: the power goes from the engine to the gearbox through fluid. There is no clutch pedal. According to BOVAG, the Dutch trade association for the motor industry, the torque converter keeps the engine running while the car is stationary and gives extra power when you pull away.

Behind the torque converter are the gears. Multi-plate clutches and brakes inside the gearbox, operated by fluid pressure, decide which gear is engaged. The control block with valves and electric solenoids is called the mechatronics unit or valve body. According to gearbox maker ZF, the pressure control valves in the mechatronics unit control the engaging and disengaging of the clutches and brakes in the gearbox.

When pulling away and changing gear, some slip in the torque converter is normal. You then see slightly higher revs than with a manual gearbox. At speed, according to BOVAG, a bridging clutch (the lock-up) closes, so there is no more slip. According to BOVAG, modern automatics often have more gears than a manual gearbox, sometimes as many as ten. With the lock-up, such an automatic can be as efficient as a manual gearbox at a constant speed, BOVAG says.

This type is fitted to many BMWs, Mercedes-Benz and Volvo models, and the EAT8 in Peugeot, Citroën and Opel models is one too. You can read how we maintain this kind of gearbox on our page about automatic gearbox flushing.

According to the ANWB, a dual-clutch automatic is in effect two gearboxes in one. One half has the even gears, the other half the odd gears, each with its own clutch. While you are driving in one gear, the next one is already lined up. According to the ANWB, a gear change takes a few tenths or even hundredths of a second.

Volkswagen, Audi, SEAT and Skoda call this gearbox DSG or S tronic. Renault has the EDC, and Ford and Volvo have the Powershift. There are two versions:

According to the German motoring magazine auto motor und sport (March 2026), the DQ250 needs an oil change every 60,000 km and the DQ381 every 120,000 km. For the dry DQ200 the manufacturer does not specify an oil change. You can see which DSG is fitted to which model on our page about DSG maintenance.

A CVT (continuously variable transmission) has no fixed gears. The ratio changes steplessly. In the best-known version, a push belt transmits the power between two pulleys. According to Bosch, which makes these push belts, the pulleys have movable cone-shaped discs. These change the effective diameter on both sides, so the engine can run in its most efficient rev range.

That is why a CVT feels different from other automatics. When you accelerate, the revs rise and stay there for as long as you keep accelerating. According to the ANWB, drivers quite often find that droning engine noise uncomfortable. According to BOVAG, that monotonous sound is part of how a CVT works. CVTs are fitted to models from Nissan, Suzuki, Subaru and Toyota, among others. You can read more on our page about CVT flushing.

A Toyota or Lexus hybrid has an e-CVT. According to the ANWB, it works with a planetary gear set and is technically different from a CVT with a push belt. Its maintenance follows the manufacturer’s schedule. We do not put an e-CVT on the flushing machine.

A robotised manual is a manual gearbox with a dry clutch, in which a computer and a hydraulic system take over the clutch work and the gear changes. According to BOVAG, this system is relatively cheap and light, and it is mainly fitted to small cars. Well-known names are Dualogic (on the Fiat 500, among others), Selespeed, Easytronic and ETG.

According to the ANWB, the drive drops out briefly during a gear change while you keep your foot on the accelerator. It feels as if the car holds back or nods. That is part of how the system works and is usually not a fault. According to BOVAG, a robotised manual and a dual-clutch gearbox should not slip while you accelerate in a gear. Slipping can point to a worn clutch plate.

The gearbox type is not shown on the Dutch registration certificate (kentekenbewijs). A garage can usually look it up using the registration number. You can often find clues yourself in the owner’s manual, in the original sales advert or on invoices for earlier maintenance. The type name helps too: 7G-Tronic, 9G-Tronic and EAT8 are conventional automatics, DSG and S tronic have two clutches, Multitronic and X-Tronic are CVTs, and Dualogic is a robotised manual.

Sources: ZF LifeguardFluid 8 product information, auto motor und sport (March 2026). “Our own advice” is the advice of Autobedrijf Willemsbrug and not a factory requirement.

Call us with your registration number on +31 10 479 00 00. We will look up which gearbox your car has, which fluid it needs and which interval the manufacturer gives. You receive a quote in advance based on your registration number. Does your automatic already have problems? Then read what to do when the gearbox goes into limp mode or when the automatic slips when pulling away.

Yes. In many cases it is. According to BOVAG, the technology in an automatic is more complex and therefore often more expensive than that of a manual gearbox. On the other hand, BOVAG says an automatic can last a very long time if the maintenance, such as changing the fluid, has been done as specified.

No. That is not necessarily the case. According to BOVAG, older automatics with few gears often used more fuel. Modern automatics with many gears and a lock-up can be as efficient as a manual gearbox at a constant speed, and according to the ANWB sometimes even more economical.

Yes. A CVT is an automatic without fixed gears. The ratio changes steplessly, so you do not feel any gear changes. Its maintenance is different from that of an automatic with a torque converter, so have the right fluid and procedure for your gearbox looked up.

No. That is not a given. According to the ANWB, the fluid lasts for the life of the car in theory, and gearbox maker ZF fills its gearboxes with fluid intended for their whole service life. Even so, ZF advises changing it after 150,000 km, and sooner with high temperatures, heavy loads or an unknown history.

According to BOVAG, an automatic can reach a high age without problems if the maintenance has been done as specified. That includes changing the fluid. A fixed number of kilometres cannot be given, because use and maintenance make a big difference.

In a robotised manual, the drive drops out briefly during each gear change. That feels as if the car holds back and is part of how the system works. If the jerking gets worse, or the gearbox slips when you pull away, the clutch may be worn and a diagnosis is sensible.

No. A conventional automatic with a torque converter can be treated with a flushing machine, if that turns out to be useful after the intake and test drive. We change the fluid in a wet DSG and a CVT following the procedure for that gearbox. We do not flush a dry DSG, an e-CVT or a robotised manual such as the Dualogic.

• ANWB: Versnellingsbak uitgelegd: soorten, werking en onderhoud (gearbox types, operation and maintenance, in Dutch)
• BOVAG (viaBOVAG): Occasion met automaat kopen? Hier moet je op letten (buying a used car with an automatic, in Dutch)
• Bosch: Pushbelt in a CVT transmission
• ZF Aftermarket: ZF LifeguardFluid 8, product information (lifetime fluid and advice to change after 150,000 km)
• auto motor und sport: DSG-Ölwechsel erklärt: Intervalle für DQ200, DQ250, DQ381 (March 2026, in German)