DSG gearbox: how a dual-clutch transmission works and what to expect

• A DSG has two clutches, one for the odd gears and one for the even gears. The mechatronic unit engages the next gear in advance, so the gearbox shifts with virtually no interruption in drive.
• Its strengths are fast shifting and direct power transfer without the losses of a hydrodynamic torque converter, which helps fuel economy.
• It's weaker when creeping, pulling away and parking, because it has to let the clutch slip. In these situations it feels less refined than a torque converter automatic. Repairs are more demanding in terms of both diagnosis and labour.
• Other brands use the same principle under different names: Audi as S tronic, Hyundai and Kia as DCT, and Renault as EDC.
• The number of gears doesn't tell you which version you're dealing with. In 2017, the Škoda Octavia III had a seven-speed DSG with dry clutches with the 1.6 TDI engine and a six-speed DSG with wet clutches with the 2.0 TDI.

In ads for used Škodas and Volkswagens, DSG is one of the most common abbreviations, and it stands for a dual-clutch gearbox. You operate a car with one just like any other automatic: select a driving mode and leave the shifting to the electronics. The differences show up when pulling away, creeping in traffic and suddenly putting your foot down. That's where the contradictory stories about dual-clutch gearboxes come from. In brisk driving they go unnoticed; when parking, they can hesitate. Once you understand how the two clutches and the preselected gears work together, you'll know which behaviour is normal and when to pay closer attention. For a comparison with the other designs, see the overview of types of automatic transmission; for driving habits, read how to drive an automatic.

DSG is the name of the Volkswagen Group's dual-clutch gearboxes. You'll find it in Volkswagen, Škoda and SEAT models. A dual-clutch gearbox consists of two sub-gearboxes, each of which receives the engine's power through its own clutch. One serves the odd gears and the other the even gears.

Say you're driving in third. The clutch for the odd gears is engaged and transmits the engine's power to the wheels. In the other sub-gearbox, fourth is already selected, but its clutch is open, so it isn't driving the car yet.

When shifting, the gearbox opens one clutch while closing the other at the same time. Torque passes smoothly from one clutch to the other, and the new gear takes over from the previous one with virtually no interruption in drive. The next gear doesn't need to be engaged mechanically at the moment of the shift, because it's been prepared in advance.

What does the mechatronic unit do?

The mechatronic unit combines the electronic control with the hydraulic actuation of the gearbox. It chooses the gears, preselects the next one, operates both clutches and coordinates their work with the engine. It takes into account the car's speed, engine revs, how you press the accelerator and the gearbox temperature.

How the car behaves depends to a large extent on its calibration. The same hardware can shift up early for economy in one model and hold the engine at higher revs for longer in another.

Preselection works best when the electronics correctly predict what you'll do next. When you're accelerating steadily, it expects a higher gear; when slowing down, a lower one. It prepares that gear, and the change then happens in a flash.

But if you suddenly floor the accelerator after a period of gentle driving, the preselected higher gear is no use. The gearbox first has to prepare a lower gear and only then can it change down. A brief delay in that situation is part of a dual-clutch's normal behaviour.

The speed of the shift itself and the speed of the response to the accelerator are two different things. The overall impression is also shaped by the engine's response and the selected driving mode.

Main advantages

A dual-clutch is at its best once the car is moving. It shifts quickly and leaves no gaps in drive when accelerating. You'll appreciate this when joining a motorway just as much as on a brisk drive along country roads.

Once the clutch is engaged, the gearbox transmits the engine's power directly, without the losses of a hydrodynamic torque converter. That's why its fuel consumption stays close to that of a manual. How much it saves compared with another type of automatic depends on the engine, the gear ratios and the control calibration.

Weaker points

At very low speeds, the gearbox has to let the clutch slip partially. This generates heat and puts more strain on the clutch. Long periods of creeping in queues therefore load it differently from steady driving, when it's fully engaged.

The interplay between the mechanical parts, two clutches and the control system is also more complex. Repairs tend to be demanding in terms of both diagnosis and labour, and the symptom often doesn't reveal the cause.

For mixed routes and regular driving outside town, a DSG offers a good combination of speed and comfort. If you spend most of your time in queues and parking, you'll notice the clutches' behaviour at low speed more.

DSG is Volkswagen's trade name. Other brands sell the same principle under their own names.

The abbreviation DCT stands for dual-clutch transmission. It's also used as a generic technical term for the whole type. Whether a particular car has a dual-clutch depends on the engine and the generation. The same model was often sold with a manual as well as with a different type of automatic.

A shared principle doesn't mean the gearboxes behave the same way. They differ in design, torque capacity and control software.

The Škoda Octavia III (2012–2020) shows just how varied the range of dual-clutch gearboxes is. The table reflects the 2017 line-up; in other model years, the engine and gearbox combinations may have differed.

So even the same model with an equally powerful engine doesn't necessarily have the same gearbox. Seven gears weren't a newer or better solution than six. It was a different design for a different engine and drive layout.

DSG comes with dry clutches as well as with wet, oil-cooled clutches. When Volkswagen introduced the seven-speed DSG with dry clutches in 2008, it designed it for engines with up to 250 Nm of torque, while the six-speed version with wet clutches was intended for engines with up to 350 Nm. The differences between the two versions are explained in detail in the article DSG: dry or wet clutch?.

A brief delay when the demand for acceleration changes suddenly is part of normal behaviour. Repeated juddering, jolts when pulling away or strong vibration when creeping are not. There's no point excusing rough behaviour with ‘that's just what dual-clutches do’.

The clutches wear, and they're put under the most strain by frequent starts and stop-start queues. At the same mileage, a gearbox from a car used mainly in town may therefore be more worn than one from a car that has done mostly motorway miles.

• Don't apply your experience of one version to all DSGs. The same badge covers different designs and calibrations.
• Maintenance is specified by the manufacturer for each version. There's no single interval for all DSG gearboxes, and the number of gears tells you nothing about it.

On a slope, hold the car with the brake, not with the throttle against a slipping clutch. The best way to find out the condition of the gearbox in a used car is a test drive and diagnostics. Both are part of the CarAudit™ inspection.

A dual-clutch is a more complex gearbox, and its faults aren't always obvious at first glance. That's why every car offered by Carvago is inspected by a technician before sale as part of the CarAudit™ inspection, which has up to 270 checkpoints, including diagnostics and a test drive. You know the result before you decide to buy the car, and Carvago stands behind the condition stated in the CarAudit™ certificate.

Every car comes with a free extended warranty. Thanks to the Carvago Blacklist, Carvago doesn't include problematic models in its offer at all.

Carvago buys the car from the original seller, becomes its owner and takes on the risks that come with it. So even with a car from a seller in another country, you buy directly from Carvago and don't have to deal with a foreign dealer yourself.

What does DSG stand for?

DSG stands for Direct-Shift Gearbox, in German Direktschaltgetriebe. It's the name Volkswagen gave to its dual-clutch gearboxes.

What do the D and S modes on a DSG mean?

D is the normal automatic mode, which favours relaxed and economical driving. In S mode, the gearbox shifts more sportily: it holds lower gears for longer and changes down more readily.

Does a car with DSG have to have paddles behind the steering wheel?

No. Paddles are a matter of the car's equipment, and the dual-clutch gearbox works without them. You can also select gears manually by moving the gear selector.

How does a DSG reverse?

Reverse is a separate mechanical gear that turns the wheels the other way. When reversing, too, the electronics control how the clutch takes up drive, so slow movement backwards feels similar to pulling away forwards.

1. https://uploads.vw-mms.de/system/production/files/vwn/003/768/file/e451eac3067123ff305d27a85f3e7eb73dd1ee6f/DSG_the_intelligent_automatic_gearbox_from_Volkswagen_2008_en.pdf?1530367024=
2. https://cdn.skoda-storyboard.com/2017/03/170307-Geneva-2017-Press-Kit.pdf
3. https://carvago.com/caraudit
4. https://carvago.com/how-carvago-works