DSG Gearboxes: Pro et Contra
What is a DSG gearbox?
From German, the abbreviation DSG means "direct transmission" (Direkt Schalt Getriebe). It is often called "preselected", due to its ability to keep the gears “ready” for the next shift. An idea of creation of such gearbox belongs to French inventor Adolphe Kegresse. In 1930s he worked in cooperation with Citroen Motors. He proposed to install a unit with two clutches and hydro mechanical control on the front-drive car Citroen Traction Avant. The new transmission was not widely used due to its very complex design for 1930s. But nowadays, with development of electronics, sciences about the materials and technology in common, the engineers returned to this concept.
DSG gearbox. How it works?
The fundamental difference between the preselective automatic gearbox and the others is in double clutch that is able to change the gears quickly. In automatic and manual transmission to change the gear, clutch disconnects the disc from the flywheel during flywheel rotation, then the driver or robotic computer selects the desired "speed", and after that, the disc gets into its place. During this time, the torque is not being transmitted to the gearbox and the car loses its dynamics. DSG system allows to get rid of such power failures. DSG principle is the work of two shafts located coaxially: the first is hollow, and the second is inside the first one. The engine is connected to both shafts through its own separate multi-disc clutch – external and internal correspondingly. On the primary (external) shaft, - there are the gears corresponding to the even shifts (2-, 4-, 6th), on the internal – the odd shifts - 1-, 3-, 5th and Reverse (“R”). When the car starts, a disc with an odd row is pressed against the rotating flywheel, and the disc with even speeds is disconnected. During acceleration, the computer module sends the command to “prepare” the second gear to disconnect the disk of the odd row at the moment of its turning on, and immediately start up the disk of the even one. Such gearbox settings allows to get rid of torque waste. Volkswagen started the manufacturing of the DSG 6 robotic gearbox in 2003. The double clutch transmission worked with use of an oil bath, thus it was called "wet" clutch. The oil in such gearbox reduces the power, increasing fuel consumption. In 2008, Volkswagen introduced a seven-speed DSG 7 with a dry clutch where this problem was solved.
Typical design of the DSG Automated Gearbox
DSG Gearbox Advantages
- The DSG gearbox due to its optimal modes of the required “speeds” switching, significantly reduces fuel consumption. Cars equipped with DSG gearbox consume about 10% less fuel than the cars with a “conventional” automatic/manual transmission.
- A distinctive feature of all such transmissions is dynamic acceleration. To switch the gear up, this gearbox needs only 8 ms – it does not have the effect of “rubber traction” as in hydro mechanical automatic transmissions.
- You can drive DSG in manual mode: change the gears manually.
- DSG transmission is 20% lighter than a similar hydro mechanical automatic transmission.
DSG Gearbox Problems
- The cost of DSG transmission affects the price of a car, significantly increasing it.
- Relatively expensive oil change (on a six-speed box) every 60 thousand kilometers. The total volume is 6.5 liters of oil.
The preselected DSG gearbox is installed on different models and brands, united under the name of Volkswagen: Audi TT (A1, A3, A4, S4, A5, A7, A6, Q5, R8), SEAT Ibiza (León, Altea), Škoda Octavia (Superb, Yeti), Volkswagen Polo (Golf, Jetta, Touran, New Beetle, Passat, Passat CC, Sharan, Scirocco, Caddy).
DSG Gearbox Issues in use
The most common problem is snatching when changing gears while driving. Clutch discs close too sharply and the car moves sharply. The second known drawback is vibration at start, clanking, grinding and other extraneous noises during gears switching. The main reason for the incorrect operation of the seven-speed transmission is its "dry" clutch. It wears out quickly due to severe operating conditions in dense urban traffic, with congestion at low speeds. Therefore, the question "how to operate the DSG?" there has one obvious answer – to avoid the "gas-brake" driving style. Other problems: wearing out of the shaft bushes, clutch release forks, broken solenoid contacts, dirt on the sensors and oil in the coolant.
How to determine a DSG malfunction when buying a used car?
- Gears are not being switched properly - the box "jumps" over them.
- Gear shifting is accompanied by blows.
- There is a noise when moving
- Vibrations at starting
- Oil leakages detected during inspection
Unfortunately, now manufacturers are generally very little concerned with the issue of cars reliability. The main vector of the automotive industry now is ecology. To save 100 grams of gasoline per 100 kilometers, various dubious technologies are being introduced. These technologies often reducing the total vehicle resource: direct injection, increasing the turbocharging pressure or cylinders compression ratio. Gearboxes are relatively “dead-end branch” of development, and DSGs, paradoxically, are now at the pinnacle of progress, as they provide efficiency (and therefore, the coveted environmental friendliness). The fact that this gearbox "lives" approximately 150 thousand kilometers is of little interest to the manufacturers.