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A look at the Dual Clutch Gearbox

This manual transmission will send even the most experienced techs looking for a refresher course.
Monday, June 30, 2014 - 07:00
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The DSG, or Dual Clutch Gearbox, is a manual transmission using a Mechatronic system to shift the transmission automatically via a double wet or dry clutch with double input shaft arrangement (Figures 1 and 2).

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TVS Engineering is a company in the Netherlands that specializes in the repair and tuning of Volkswagen/Audi DSG transmissions. TVS began seeing a need to modify both the clutch assembly and programming approximately 10 years ago (Figure 3). Premature clutch failure was on the rise due to a turbo being mounted to these vehicles (Figure 4). They currently repair about 1,500 of these a year through 18 dealers around the world selling clutches, Mechatronic, gearboxes and software (Figures 5 and 6). This article is the result of having and interview with Ronald Logmans, the software engineer for this company.

Currently, there are four generations of high production DSG transmissions on the road worldwide (others are on their way). They could be either longitudinally (AWD) or transversally (FWD) mounted. Of the four generations, one is a six-speed while the remaining three are seven-speed transmissions. The names of these different transmissions are as follows:

2003 - DQ250 – 6 speed wet – F/AWD

2008 - DQ200 – 7 speed dry – FWD

2008 - DL501 – 7 speed wet – AWD

2010 - DQ500 – 7 speed wet – F/AWD

The D represents Dual Shift Gearbox (DSG), the L is for longitudinal (RWD) and the Q is for transversely mounted (F/AWD).

FIGURES 1-3

Besides the various generations and designs, what makes this a bit more confusing is that there does not seem to be any logical pattern as to application. An Audi A3 could be fitted with a 1.8L engine and have either a DQ200 or a DQ250.

The first DSG was a six speed “wet” clutch design that started in 2003 for the Audi TT. This transmission is referred to as the DQ250 (02E) and had AWD. The second generation began in 2007. It was the DQ200, which is a seven-speed double “dry” clutch design that came as a front wheel drive only. There are no AWD with a dry clutch design. It is the only dry clutch unit in the DSG family, and of all the DSGs, this is the most problematic of them all. It also was the most sold transmission worldwide except here in the United States. Globally, it is in two Audi vehicles (A1 and A3) and 16 different Volkswagen vehicles (Beetle, Bora, Caddy Van, Golf, Jetta, Lavida, Passat, Polo, Sagitar, Scirocco, Sharan, Tiguan, Touran and UP). Skoda and Seat models use the DQ200 and the DQ250.

The main failure with this transmission is the clutch wearing out. Signs of failure begin with feeling a judder or shudder on mild acceleration after deceleration from 18 mph to 3 mph during a 2nd gear hold, especially in turns. This DSG holds 2nd gear even longer than the others during deceleration. The computer commands the clutch to slip as the vehicle is nearing a stop to prevent engine surge and stalls. The design of this dry clutch assembly, as well as it being a dry clutch, along with this long hold 2nd gear slip strategy, the clutch assembly overheats. This is especially true during acceleration before coming to a complete stop.

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