What is a Dual Clutch Transmission?

Like everybody, you learned on either a manual or an automatic transmission. You still may prefer one over the other. But you can have the best of both with a dual clutch transmission (DCT), also referred to as a “twin-clutch” or “automated manual” transmission.

The dual clutch transmission or DCT allows you to have the best of both types, it is a gearbox designed to improve the driving experience by reducing acceleration times, fuel consumption and giving greater comfort to the driver.

What is a dual-clutch transmission? It is a type of automated manual transmission in which two independent clutches are used to transmit engine torque. One of these clutches acts on the even gears and the other on the odd gears for smooth, fast and better engaging gear changes.

How Does a Dual Clutch Transmission Work?

The dual-clutch transmission design has been around since before World War II, but it wasn't until the 1980s that the design became a reality and it wasn't until 2003 that it was introduced in a Volkswagen production road car.

The dual-clutch transmission is a kind of hybrid between a manual and automatic transmission. In the manual gearbox, the driver must depress the clutch to shift smoothly. On the other hand, in the DCT gearbox there are two clutches instead of one, these share the same space, but are separate shift shafts to act on different gears to have a smoother transition and higher speeds.

In addition, this system works with several integrated computers, which means that no clutch pedal is needed so that the driver does not have to activate the shift lever manually and the process is automated.

These clutches can be dry or immersed in oil to better resist heat. It is important to note that, although the DCT transmission has two clutches, it does not have a clutch pedal and the computer sends commands to the internal system to make the shifts.

In DCT transmissions, the larger K1 clutch transmits torque via a solid shaft to odd-numbered gears 1, 3 and 5, while the smaller clutch or K2 sits parallel to K1 and operates the gears for even-numbered gears 2, 4, 6 and reverse. Although both clutches are continuously active, only one is connected to the engine at any given time.

The shifting process occurs as each clutch comes into play, i.e. K1 disengages and K2 engages. For example, when accelerating in third gear, fourth gear is already engaged in the second transmission structure to make the shift smoothly, in tenths of seconds and without interrupting speed.

Dual-clutch transmissions have the characteristic of shifting from one gear to another dynamically, smoothly, quickly and comfortably because the shifts are barely perceptible to drivers.

Why “Dual”?

Like its name suggests, a DCT vehicle literally has two transmissions. When one is engaged, the other is pre-loading or “prepping” for the next gear. One transmission usually handles the odd-numbered gears, while the other is responsible for the even-numbered ones; reverse gear is controlled by one or the other.

The purpose behind DCTs is to change gears without interrupting the power flow from engine to transmission. By having the next gear on “standby,” when the active one disengages, gears switch more smoothly and the car is less likely to lurch. DCTs are particularly suited for high-speed driving, and in fact, that’s where the concept originated—in the racing industry.

However, DCTs didn’t generally become available for passenger vehicles until the turn of the century. Now they’re commonly available in various models of sports and luxury vehicles, including Audi, Nisson, Volkswagen, Porsche, and Mercedes. They’re also used in heavy-duty commercial vehicles, such as trucks and large farm equipment, and recently are becoming more popular in lower-priced vehicles.

Dual clutch transmission (DCT) pros and cons

It’s a tough call: DCTs have advantages and disadvantages. You might like DCTs because:

• There’s no manual shifting or clutch pedal to manage.
• They offer better fuel economy than other transmission types, as there is no torque converter.
• Shifting between gears is smoother, thanks to the dual gearboxes.
• They’re really good for higher-speed and highway driving.
• The DCT transmission is ideal for sport utility vehicles, which are driven on the road or at high speeds.
• They are vehicles that have a constant power flow in the engine, thus increasing fuel efficiency compared to standard vehicles.
• Gear changes are quicker and there is hardly any loss of speed with shifting.
• Greater temperature control.

On the other hand, you might not like DCTs because:

• They don’t always shift smoothly at very low speeds.
• They’re more expensive than standards or automatics and they cost more to repair or replace.
• Two transmissions take up additional space under the hood.
• For some drivers, fast shifting is abrupt and uncomfortable.
• Reverse and forward gearing, as well as initial acceleration can feel hesitant.
• It requires more oil in the gearbox, which makes it more costly to maintain.
• When the gear is engaged the other is in standby, making braking at a traffic light more abrupt, especially when driving in small towns.

Having said all of that, choosing your transmission type is just one of many choices you have when you’re shopping for a vehicle nowadays. It all boils down to your preferences, your budget, and what you intend to use the vehicle for.

Comparison with Other Types of Transmissions

Each type of transmission offers a different driving experience, the most common of which are discussed below:

Conventional Automatic Transmission

The conventional automatic transmission is connected to the engine through a hydraulic torque converter and a set of gears that adapt the engine speed to remain in a range and produce the amount of torque needed to make the gear change.

Manual Transmission

Vehicles with manual transmission are characterized by three pedals, the brake, accelerator and clutch pedals. The driver must depress the clutch pedal to engage the gears by means of the shift lever. The operation is complex as it requires the driver's coordination.

Continuously Variable Transmission (CVT)

The CVT transmission uses a system of pulleys and belts instead of gears. The motor turns one pulley while the other is connected to the rest of the transmission, thus moving the vehicle's wheels at a constant rpm without loss of power.

Applications of Dual Clutch Transmission

In recent years, the popularization of automatic transmissions has led more manufacturers to include them in their vehicles. Brands such as Mercedes Benz, Audi and BMW have opted for the DCT transmission for its benefits in terms of speed and efficiency. DCT can be found in:

Passenger Vehicles

The DCT offers fast, smooth and comfortable gear changes in passenger cars or small, sporty and everyday cars.

Heavy Trucks

The DCT transmission is also used in SUVs and cargo vehicles such as tractors and trucks to improve the driving experience, increase safety, precision and reduce wear. In addition, it improves fuel efficiency by maintaining power through the gears.

Maintenance and Care of Dual Clutch Transmissions

To prolong the life of the DCT transmission, it is recommended:

• Do not place the lever in neutral when stopping at traffic lights for a couple of minutes, the system automatically detects that the vehicle is stopped or the brake is being applied and disengages the clutches automatically.
• Keep the brake pressed when stopping on slopes and avoid letting the gearbox do the braking to avoid unnecessary wear or friction.
• Avoid abrupt acceleration and braking so that the gears run correctly.
• Monitor the condition of the transmission oil and have the vehicle serviced promptly. The frequency of ATF change varies according to the manufacturer in periods between 40,000 and 60,000 miles.
• Check the vehicle every day for any possible changes. In case of light red oil leaks around the gearbox or under the vehicle, it is essential to take it to the mechanic.
• When changing the ATF, choose the correct product for the vehicle, which is usually indicated in the owner's manual. In addition to changing the ATF, it is recommended to change the filter so that impurities do not pass from the old oil to the new one.

Have Transmission Needs?

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