Twin-clutch Gearbox

A Twin-clutch gearbox is a semi-automatic transmission with separate clutches for odd and even gears. Shifts can be accomplished without interrupting power by transferring torque between these two clutches. A dual clutch gearbox eliminates the torque converter, which is a major source of parasitic loss in a traditional automatic transmission. This type of gearbox was invented by Andolphe Kégresse just before the outbreak of World War II.

Essentially, the engine drives two clutch packs simultaneously. The outer clutch pack drives gears 1, 3, and 5 (and reverse). The inner clutch pack drives gears 2, 4, and 6. The synchronizers that select an odd gear can be moved while driving in an even gear and vice versa. Dual clutch transmissions that are currently on the market use wet multi-plate clutches, similar to the clutches used in traditional automatic transmissions. Versions that use dry clutches, like those usually associated with manual transmissions, are rumored to be in development by several manufacturers.

BorgWarner is currently the leading manufacturer of this type of transmission. They are most commonly sold under the name Direct-Shift Gearbox, as sold by Volkswagen Group. In August 2005 BorgWarner, who call their technology "DualTronic", signed further agreements with two other (unnamed) European automotive manufacturers to incorporate their gearbox.