Once upon a time, all automatic gearboxes operated using the same basic principles. But nowadays, there are several different types out there – and with most manufacturers coming up with different brand names for their own particular offerings, it’s becoming rather confusing to work out what’s what.
Help is at hand, though, with our automatic gearbox guide, which will help you navigate your way through the myriad types of auto gearbox currently on sale and decide which is best for you.
What is a torque-converter automatic?
This is the traditional auto gearbox – the one you’d have found in pretty much every automatic car 20 years ago – and it’s still very commonplace today, particularly in prestige cars.
The name “torque converter” refers to the bit of technology that transmits power through from the engine to the gearbox itself – like the clutch does in a manual car.
But rather than an actual physical connection, as you’ll find with a clutch, the torque converter uses thick hydraulic fluid to transfer drive from the engine to the gearbox.
Because of this fluid link, torque converter automatics are usually able to change gear smoothly. And because this sort of technology has been around for so long, it’s proven itself dependable.
The downside is that the torque converter isn’t actually a very efficient way of transferring the engine’s power. As a result, this type of gearbox can be a little heavier on fuel than others, and can also be slow to change gear.
Also known as: ZF 8-speed, ZF 8HP, ZF 9-speed, ZF 9HP, 9G-Tronic, Geartronic
Choose if: you want a smooth, reliable automatic gearbox that keeps engine noise to a minimum
What is an automated manual?
As its name suggests, a car with an automated manual gearbox has a manual gearbox that’s operated electronically.
But you won’t find a clutch pedal and gearstick moving themselves around as if by magic. Most of the time, the shifter looks just like a normal automatic, and there’s no clutch pedal at all.
Under the skin, though, this gearbox works much like a manual – except it’s an electronic control unit deciding when to change gear, rather than the driver.
When it decides the time is right, it disengages the clutch automatically, selects a new gear, and then re-engages the clutch.
The problem is that it’s quite a big ask for the gearbox to do all that both quickly and smoothly. As a result, this type of gearbox is usually either slow to change gear or jerky – or, in the worst cases, both.
Also known as: robotised manual, clutchless manual, Tiptronic, SMG, ASG, ETG, EGC, EAT
Choose if: you want an automatic gearbox that doesn’t cost very much as an optional extra
What is a dual-clutch automatic?
This relatively new type of automatic gearbox was first used in the Audi TT and works much like an automated manual, except a dual-clutch gearbox has – you’ve guessed it – two clutches.
The idea is that the control unit can line up the gear it thinks you’re going to need next on one clutch while the other is still being used to drive the car. This means it can change gear more smoothly, and extremely quickly.
However, it is possible to catch a dual-clutch gearbox out. There’s sometimes a slight delay as the first clutch engages, for example, which can make low-speed manoeuvring a little awkward.
The other downside of dual-clutch automatics is their complexity; in recent years, older dual-clutch units have gained a reputation for poor reliability and some have needed costly repair work.
Also known as: twin-clutch, double-clutch, DSG, DCT, PDK, R-tronic, Powershift
Choose if: you want the automatic gearbox that combines fast gear changes with good fuel economy
What is a CVT gearbox?
A CVT, or “continuously variable transmission”, is odd in that it doesn’t actually have cogs like a normal, traditional gearbox.
Instead, inside a CVT gearbox you’ll find two cones, one attached to the engine and the other to the wheels, and linked by a belt which runs between them.
As you accelerate, the cones move toward and away from each other, adjusting the position of the belt and, in turn, the gearing.
The result is a very efficient gearbox, because the gearing can be adjusted almost infinitely. This means the engine can be kept at the optimum speed at all times.
What’s more, because there are no fixed gears, there are no gear changes either – and that means smooth acceleration without any jolts.
But a CVT isn’t without its downsides. If it’s matched to a weedy engine, it’ll hold the engine at high revs as you accelerate, to extract the most power – and that can mean you hear a lot of engine noise inside the car.
Also known as: belt-and-pulley, Xtronic, E-CVT, Multitronic
Choose if: you want the smoothest acceleration with good fuel economy, and don’t mind a bit of extra engine noise
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