Automatic gearboxes are a popular selection in the UK new car market, particularly when motorists are getting an executive or large family car. But did you know there's a variety of different ways manufacturers make automatic gearboxes?
When looking to buy a car with an automatic gearbox, then you’ve likely seen different names used for them by different manufacturers. Nowadays, you can come across terms like CVT, DSG, twin-clutch and dual-clutch.
Here we explain the different types of automatic gearbox you can find in today's car market and the differences that are worth knowing about.
Conventional automatic gearbox
All automatic gearboxes chooses what gear a car should be in, based on the current speed at the time, without the driver’s input. There’s no conventional clutch pedal included and the gear stick is only used to choose forward (or ‘Drive’), reverse, neutral and ‘Park’.
With conventional automatics, the engine is linked to a torque convertor, allowing the engine to rotate (in other words function properly) even when the road wheels are still.
CVT stands for Continuously Variable Transmission, but these are also known as a Stepless automatic gearbox.
The main difference with a CVT gearbox compared to a conventional automatic, is that its design allows it to easily change its gear ratios. It’s easier therefore to strike a balance between performance and efficiency. In fact, cars with CVT can be just as efficient as their manual equivalents when used for city driving, although some efficiency is lost when on faster roads.
Also, while the gear changes should feel smooth, the engine revs will rise to those required for optimum power and stay there until the car’s speed ‘catches up’. This can feel a bit like a slipping clutch and make a car with a CVT sound pretty noise at times.
Dual-clutch or twin-clutch automatic gearboxes use two clutches, with one clutch assigned to odd-numbered gears and the other used for even-numbered gears.
When a car with a dual-clutch gearbox engages, say, third gear, the fourth gear will be ‘pre-selected’ by a computer. With the aid of hydraulics, the gearbox switches from clutch to another as fast as possible.
Examples of dual-clutch gearboxes found in new cars today includes BMW DCT, Mercedes-Benz Speedshift, Porsche PDK, Volkswagen Group’s DSG and PowerShift used by Ford and Volvo.
The advantage of dual-clutch gearboxes is that they should offer gear changes that are so seamless they are barely noticeable. They can be quite expensive, however. While a conventional automatic gearbox typically costs about £1,000 to add to a car, a dual-clutch can cost closer to £1,500.
Clutchless manual gearbox
This type of manual gearbox uses electric motors to take care of the clutch work for the driver.
Drivers, however, can manually override this function using an onboard lever or paddles on the steering wheel.
Some of the current examples of clutchless manual gearboxes around include Honda iShift and Suzuki’s EZ Drive.
Clutchless manual gearboxes are cheaper than a conventional automatic gearbox, costing about half the price in fact. However, the automatic changes from the electric motors can turn out to be jerkier compared to manual shifts or other automatic ‘boxes.