Car Companies May Love DCTs, But Dual-Clutch Transmissions Have Disadvantages Too

Dual-clutch automatic transmissions have exploded in popularity over the last two decades. They're used in performance cars of all types, from the Volkswagen GTI and Hyundai Elantra N to the BMW M2 and McLaren 720s. But dual-clutch transmissions have also found homes in normal cars. Hyundai and Kia are big users of dual-clutch transmissions in models like the Kia Seltos crossover and the N-Line versions of the Hyundai Sonata and Elantra.

Automakers use dual-clutch transmissions for good reasons. Compared to a normal automatic a dual-clutch has more than a few benefits, mainly increased acceleration, quicker gear changes and better fuel economy. It took automakers a while to warm up to the idea of the dual-clutch, though. The dual-clutch transmission was invented over 80 years ago by French engineer Adolphe Kegresse, and it wouldn't be until the early 2000s that the dual-clutch would start to get traction with automakers.

Volkswagen was one of the first automakers to bring a dual-clutch transmission to market with the Mark 4 Golf R32. This was followed by other performance models in the late '00s like the R35 Nissan GT-R, Bugatti Veyron and Mitsubishi Evolution X. Despite this use in high-performance vehicles and the obvious performance advantages, dual-clutch transmissions have a few disadvantages as well.

You can tell how complicated dual-clutch transmissions are just from the name. In a conventional manual transmission, a driver operates the clutch pedal to change gears. When pressed, the clutch pedal disconnects the engine from the gearbox, causing a brief power interruption while the driver selects the next gear with the shifter. When this happens, a toothed collar moves from one gear wheel to the next gear wheel, which is a different size. To prevent the gears from grinding, synchronizers match the gears up. Once the clutch pedal is released and the gear change is completed, the engine is reconnected to the driver shaft and the engine's power is sent to the wheels.

A dual-clutch transmission basically does all that automatically without a clutch pedal, but it's way more complicated. As the name suggest, there are two clutches: one clutch controls the odd gears while the other controls the even numbered ones. Assisted by a bunch of electronics and hydraulics, the gears are able to change like an automatic transmission but without the interruption of power that happens in a normal manual transmission. Things get more complicated when you factor in things like wet dual-clutch transmissions, which cover parts of the transmission's inner workings in lubricating fluid to reduce heat and friction. So there's more to go wrong, and more money out of your pocket if something needs to be fixed or replaced. Ford owners know this first-hand thanks to the nightmare that was the PowerShift transmission — some owners reported getting repair bills of a couple thousand bucks just to replace the clutch.

DCTs aren't usually stand-alone options by themselves, save for a few exceptions. The F87 BMW M2 offered buyers the choice of either a standard six-speed manual or an optional seven-speed dual-clutch transmission. It wasn't cheap, though, costing $2,900. Other automakers just factor in the price of the transmission with the overall cost of the car, but it'll still be a bit more than cars that don't come with the transmission. Take the Hyundai Elantra N-Line, for instance. This Honda Civic Si competitor comes with a 201-horsepower turbocharged engine and a seven-speed wet dual-clutch transmission. Despite being positioned as one rung down from the top-of-the-line Elantra Limited, the Elantra N-Line is the most expensive trim in the lineup. There's a $2,200 difference in price between the N-Line and Limited; that difference grows to $3,150 if you compare the N-Line with the Elantra SEL Convenience.

One of the biggest drawbacks of a DCT is the smoothness of the gearshifts. You can have lightning fast shifts to your heart's content all day long, especially if you're really into the car's performance envelope. Once things tone down and get back to normal, it can feel like you're getting kicked in the back by shifts. Some people may even think something is wrong with their car. Others may experience more jerkiness when the car is cold. There's no need to worry, though, because this is just a normal part of DCT operation and a downside of those fast shifts. At higher speeds, the computer can anticipate that you're going to need that next gear ASAP, but low speeds can trip the computer up, causing a delay and jerkiness because it can't anticipate what gear you're needing next.

Even with these drawbacks, DCTs are still fantastic transmissions. And unless you're driving something that the manufacturer just didn't get right out of the gate, none of this should scare you away from owning one. Just like any other component of a vehicle, treat it right and service it regularly and you shouldn't encounter any problems.