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What Is a SelectShift Transmission?

by Richard Rowe

Conventional automatic transmissions have their benefits in terms of convenience, but manuals have always been better from a mechanical perspective. The Ford SelectShift transmission is one of the newest generation of gearboxes that combines the best of both -- and then some.

Construction

The SelectShift is a "dual-clutch" transmission, the same type used in some of the highest-end performance cars on the road today. A DCT is literally just two dry-clutch, computer-controlled manual transmissions placed side-by-side, connected to each other with a common input shaft and common output shaft. One transmission carries the odd-numbered gears, and the other the even-numbered gears. These transmissions have been around in theory for more than 70 years, but weren't practical without computer controls. In the 1980s, Porsche rediscovered the concept, and did the lion's share of modern development. Most DCTs, including the SelectShift, are direct inheritors of Porsche's design work.

Function

A DCT works by "pre-selecting" gears. The vehicle starts out in first gear, with the clutch on the left-hand -- odd-number -- transmission engaged, and the clutch on the right-hand transmission disengaged. During the upshift, the right-hand transmission's clutch engages, sending power to second gear as the left-hand clutch disengages and releases first gear, and on and on. The end result is a completely seamless, crisp and uninterrupted delivery of power, with absolutely no lag between gears. It's a transmission with almost all the benefits of both a manual and an automatic, and ends up better than either in almost every respect. The only downside: DCTs like the SelectShift are twice the transmission, so they're bigger, heavier and more expensive than their more garden-variety counterparts.

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