With this type of gearhead there is certainly no shortage of designations. First of all, it belongs to the group of sequential ones. This means that the gears are not arranged according to the H-scheme, but are all actuated one hehind the other by the same operation. As an example you can take two-wheelers, where from the second gear on the higher ones are engaged by operating a foot lever.

Of course, nothing is to be 'engaged' with this transmission, at least not by foot or hand, which is why it can be considered an automatic transmission. The only way to distinguish it from the most known ones here is to call them torque converter automatic transmissions, but this does not cover all of them anymore. In any case, this transmission here definitely has no torque converter.

And now comes the name we want to use from now on, namely 'Double-clutch transmission' (DCT). VW, as the first manufacturer of such transmissions in mass production from 2003, calls it Direct Shift Gearbox (DSG). We will alternatively use these abbreviations.

Why was it given this name by VW? This was probably not least for advertising reasons. They wanted and still want to point out the particularly short switching times. DCT's go very well with sporty vehicles such as a VW Golf GTI. As a passer-by, you must have experienced how this car accelerates one gear after the other without any pause.

Although one had to wait a long time for such a transmission, the principle is quite simple and easy to follow. In short, in a normal manual transmission, the even gears (blue, dark) on one side and the odd (green, lighter) ones on the other are combined into a partial transmission and each is assigned to one of the two clutches, which can be operated separately. In spite of similarity, this is not a classic two-disk clutch.

And why is it possible to switch up so quickly now? Because, for example, when in stationary operation the clutches are open, not only is the first gear can be engaged the rightmost shift sleeve to the right, but at the same time the second gear by shifting left the second shift sleeve on the the left side. And why does the transmission not lock? Because for starting only the left of the two clutches is engaged.

The right clutch remains open and waits for the opportunity to shift into second gear. As this is already engaged, you only have to disengage the left clutch and engage the right one. If the sequence is too rapid, wear and tear is pre-programmed. If there is too much pause between the respective functions of the two clutches, the sporty drivers will complain.

With the transmission at the top, the six gears are realized on two shafts when reverse gear is omitted. From the left-hand clutch, it goes through the hollow shaft for gears 2, 4 and 6 The now shown gearbox is particularly short due to its three-shaft design. A fourth shaft is used to realize the reverse gear. In addition, the single-disk dry clutches gave way to multi-plate clutches. They are available in dry and wet design, i.e. running in oil.

1. Gear
The right sliding clutch on the lower (rear) shaft is shifted to the right and transfers the torque, because the green multiple-disc clutch has been engaged. Almost at the same time the left sliding clutch on the lower (rear) shaft was already shifted in preparation, to the left.

2. Gear
The blue multiple-disc clutch is the one, that disengages the green one. That way, the second gear is engaged without a break. In preparation for the third gear, the right sliding clutch is shifted to the left.

3. Gear
Again a clutch change, and afterwards, for the preparation of the fourth gear, the left sliding clutch is shifted. The first four speeds are transferred through the lower (rear) shaft and the smaller spur gear to the final drive.

4. Gear
If the blue clutch is now engaged again, the lower rear shaft is included in the power transmission for the last time. On the upper (rear) shaft the right sliding clutch is already preparing for the use of the fifth gear.

5. Gear
Now the upper (rear) shaft which is also connected, through a larger spur gear, with the final drive, is involved in the other gears. The right sliding clutch transfers the torque, the left one is engaged for the sixth gear.

6. Gear
The highest gear is reached. Actually, one could leave the sliding clutch of the fifth gear as it is. The zero position should make it clear that here no further preparation is necessary.

Reverse gear
Not only three shafts and mutually, meshing gearwheels are found in the compact-construction gearbox. A fourth one provides for the change in the rotary direction. Of this, one sees only the circulation wheel between both gearwheels which are positively connected by the left sliding clutch to the upper rear shaft. While driving in reverse the first gear can be already engaged so that, to drive forwards again, only the clutch must be changed.