The DSG gearbox is basically a manual gearbox that is controlled electronically. It has two clutches instead of the usual one. One clutch acts on the odd numbered gears (1,3,5,7) and the other clutch acts on the even gears (2,4,6 and reverse). It operates in the same fashion as a normal manual gearbox and is fitted with a normal manual gearset. However the job of engaging and disengaging the clutches and the job of shifting the gears into place is done by the mechatronics unit. This unit has a computer that receives electrical signals from sensors that determines when to use the clutch and when to change the gears. In essence the mechatronics replaces the job done by your left foot (clutch) and left arm (gearshifter). It moves the clutch and gearshifter by using hydraulic pressure that is built up by a pump built into the mechatronics unit. In the 6 speed DSG it uses the gearbox oil to build up the hydraulic pressure and in the 7 speed DSG it uses an internal electrical pump and hydraulic fluid to build up the pressure. The actual gearbox part is filled with VW's manual gearbox oil. In the 7 speed it is the same gearbox oil that all the manual VW gearboxes have in them. Because of the two clutches, while one clutch is engaged and is transmitting power to the wheels the next gear in sequence can be selected at the same time because its clutch is disengaged. When it is time to change gear the first clutch disengages as the second one engages. So there are always two gears selected but only one is actually transmitting power. There are no torque converters in a DSG.
Edited by: plbxr
