[M3-FAST]

Not sure what 'linkage' there is between the two clutches Helen? They both operate independently.

The twin-clutch gearbox is essentially two separate gearboxes with a pair of clutches between them. One gearbox provides odd-numbered speeds (ie first, third and fifth gear), the other provides even-numbered speeds (second, fourth and sixth). When the car starts out, the "odd" gearbox is in first gear and the "even" gearbox is in second gear. The clutch engages the odd gearbox and the car starts out in first gear. When it's time to change gears, the transmission simply uses the clutches to switch from the odd gearbox to the even gearbox, for a near-instant change to second gear. The odd gearbox immediately pre-selects third gear. At the next change the transmission swaps gearboxes again, engaging third gear, and the even gearbox pre-selects fourth gear. The twin-clutch transmission's computerized controller calculates the next likely gearchange based on speed and driver behaviour and has the "idle" gearbox pre-select that gear.

There were lots of instances of SMG gearboxes giving up the ghost, these gearboxes are different to DSG's because they are essentially a manual box that uses a solid coupling (the clutch) between the engine and gearbox. The chief drawback of the SMT is the same as that of a manual: In order to change gears, the engine and transmission must be disconnected, interrupting the flow of power.

I am not being defensive because I own a DCT equipped car, but I really have not heard of anyone with said gearbox having failures where the gearbox 'self destructs?'

There has been failures on the M3 forum, but mainly electronic errors that are fixed without a gearbox repair required.

DSG gearboxes are the future and more and more cars are being fitted with them, with the technology now being applied to cars such as Polo's and Fiesta's (Ford has launched the 'smartshift' DSG type 'box) - these cars are designed for high mileages and urban driving with reliability being paramount.

Just about every large volume performance car manufacturer (Lambo, Ferrari, Porsche, etc....) have a DSG box. Jaguar desperately needs to catch up if they want to compete in that market.