A direct-shift gearbox (DSG, ) is an electronically controlled, dual-clutch, multiple-shaft, automatic gearbox, in either a transaxle or traditional transmission layout (depending on engine/drive configuration), with automated clutch operation, and with fully-automatic or semi-manual gear selection. The first dual-clutch transmissions were derived from Porsche in-house development for the Porsche 962 in the 1980s.
In simple terms, a DSG automates two separate "manual" gearboxes (and clutches) contained within one housing and working as one unit. It was designed by BorgWarner and is licensed to the Volkswagen Group, with support by IAV GmbH. By using two independent clutches, a DSG can achieve faster shift times and eliminates the torque converter of a conventional epicyclic automatic transmission.
Overview
Transverse DSG
At the time of launch in 2003, it became the world's first automated dual-clutch transmission in a series-production car, in the German-market Volkswagen Golf Mk4 R32, and shortly afterwards worldwide, in the original Audi TT 3.2. and the 2004+ New Beetle TDI. For the first few years of production, this original DSG transmission was only available in transversely oriented front-engine, front-wheel-drive and Haldex Traction-based four-wheel-drive vehicle layouts.
The first DSG transaxle that went into production for the Volkswagen Group mainstream marques had six forward speeds (and one reverse) and used wet/submerged multi-plate clutch packs (Volkswagen Group internal code: DQ250, parts code prefix: 02E). It has been paired to engines with up to of torque. The two-wheel-drive version weighs . It is manufactured at Volkswagen Group's Kassel plant, with a daily production output of 1,500 units.
At the start of 2008, another world-first seven-speed DSG transaxle (Volkswagen Group internal code: DQ200, parts code prefix: 0AM) became available. It differs from the six-speed DSG, in that it uses two single-plate dry clutches (of similar diameter). This clutch pack was designed by LuK Clutch Systems, Gmbh. This seven-speed DSG is used in smaller front-wheel-drive cars with smaller-displacement engines with lower torque outputs, such as the Volkswagen Golf Mk6, Volkswagen Polo Mk5, and the new SEAT Ibiza. It has been paired to engines with up to . It has considerably less oil capacity than the six-speed DQ250; this new DQ200 uses just of transmission fluid.
In September 2010, VW launched a new seven-speed DSG built to support up to , the DQ500.
Audi longitudinal DSG
In late 2008, an all-new seven-speed longitudinal S tronic version of the DSG transaxle went into series production (Volkswagen Group internal code: DL501, parts code prefix: 0B5). Initially, from early 2009, it is only used in certain Audi cars, and only with longitudinally mounted engines. Like the original six-speed DSG, it features a concentric dual wet multi-plate clutch. However, this particular variant uses notably more plates – the larger outer clutch (for the odd-numbered gears) uses 10 plates, whereas the smaller inner clutch (driving even-numbered gears and reverse) uses 12 plates. Another notable change over the original transverse DSGs is the lubrication system – Audi now utilise two totally separate oil circuits. One oil circuit, consisting of , lubricates the hydraulic clutches and mechatronics with fully synthetic specialist automatic transmission fluid (ATF), whilst the other oil circuit lubricates the gear trains and front and centre differentials with of conventional hypoid gear oil. This dual circuit lubrication is aimed at increasing overall reliability, due to eliminating cross-contamination of debris and wear particles. It has a torque handling limit of up to , and engine power outputs of up to . It has a total mass, including all lubricants and the dual-mass flywheel of .
This was initially available in their quattro all-wheel-drive variants, and is very similar to the new ZF Friedrichshafen-supplied Porsche Doppel-Kupplung (PDK).