What Is a Dual-Clutch Transmission?
This gearbox combines the efficiency of a manual with the convenience of an automatic.
Manuel Carrillo III/Capital One
Article QuickTakes:
A dual-clutch transmission (DCT) is a type of automatic transmission that is most commonly found in performance vehicles and efficiency-focused models. Compared with conventional automatic gearboxes, DCTs typically have lower parasitic losses, which improves fuel economy and performance. These transmissions are also capable of incredibly fast shifts measured in milliseconds, which helps acceleration. In certain models, they’re also capable of performing dramatic launch control starts, in which the engine revs to high rpms while the vehicle is stationary for the quickest zero-to-60-mph times. When the driver lifts off the brake pedal, the transmission engages and the car rockets off the line.
Like other automatic transmissions, a DCT can change gears without input from the driver, but most examples also allow the driver to select gears for themselves if they like, either via shift paddles behind the steering wheel or by using the shift lever. This feature provides the driver with more control, allowing them to change gears in anticipation of a corner or before overtaking, making performance driving more fun and engaging.
How Does a Dual-Clutch Transmission Work?
The transmission in your car allows the powertrain and the drive wheels to rotate at different speeds. Not only does this improve acceleration performance and cruising efficiency, but also, this is necessary so that the engine doesn’t stall when you come to a stop. The major differences between types of transmissions are how they decouple from the engine and how they change gears.
If you were to crawl under a car, extract its dual-clutch transmission, and crack open the housing, you’d find a set of gears and shafts that look quite similar to the insides of a manual transmission. Both gearboxes interface with the engine through a clutch, which presses rotating discs together—one set attached to the engine, another set attached to the transmission and drive wheels—with increasing force until they are spinning at the same speed. But unlike a manual gearbox, which has one clutch that the driver must operate via a pedal, a DCT has two clutches—hence the name—and relies on a computer, not the driver, to actuate them.
Why would you want a dual-clutch transmission? In a word, speed. Picture a DJ switching between records. If they have just one turntable, they’ll have to stop the record, pull it off, drop the next one on, and then get the new vinyl spinning before you can hear the song. Meanwhile, everyone stops dancing and an awkward silence creeps over the scene. Doesn’t sound like a very fun party, does it? If, however, the DJ has two turntables, they can have one record playing while they cue up the next, get it spinning, then crossfade between the two with no downtime or loss of party momentum.
Conceptually, you can think of a DCT as a pair of robotic manual transmissions in one package. Transmission A is dedicated to the odd-numbered gears (1, 3, 5, etc.), while Transmission B handles even-numbered ratios (2, 4, 6, and so on). If the car is directing power to the drive wheels through Transmission B to accelerate in second gear, Transmission A is standing by ready for the handoff to third. The transition happens when the clutch of Transmission B opens and, simultaneously, the clutch of Transmission A engages. A DCT does all of this thanks to the impeccable timing of a computer, providing precise shifts quicker than a human could ever achieve, and with minimal wasted energy or interruption of power to the wheels.
What Cars, Trucks, and SUVs Use Dual-Clutch Transmissions?
DCTs go by various trade names depending on which brand is selling them. In the early-aughts, Volkswagen became the first company to put them into wide use, installing its Direct-Shift Gearbox (better known as DSG) in the Europe-market Golf R32, followed by the original Audi TT and various other VW products, including the GTI and Jetta GLI. After experimenting with a DCT for competition in the ’80s, Porsche developed its PDK (Porsche Doppelkupplungsgetriebe, literally Porsche double-clutch gearbox) for use in road cars like the 911 and 718 Boxster. For a while, automakers tended to reserve DCTs for high-performance vehicles, where the need for speed justified the cost of a more complex transmission, but over time, this kind of gearbox has made its way into mainstream vehicles and those with an efficiency focus. You can now find a DCT in everything from a $25,000 Hyundai Ioniq Hybrid to a $3.8 million Bugatti Chiron hypercar.
