Who invented the dual-clutch transmission concept in 1939?

Adolphe Kégresse invented the dual-clutch transmission concept in 1939. His design envisioned two clutches and separate gear paths so the next gear could be prepared before the current gear was disengaged, reducing interruption of power delivery.

Kégresse intended the system for the Citroën Traction Avant. He had already become famous for the Kégresse half-track system, developed for difficult terrain and later used on Citroën vehicles. After leaving Citroën, he pursued other mechanical inventions, including an early dual-clutch gearbox concept. Financial constraints prevented the 1939 design from becoming a successful production system.

The basic principle is still used in modern DCTs: one clutch serves odd-numbered gears and reverse, while the other serves even-numbered gears. When the car is moving in one gear, the next gear can be selected on the alternate shaft; control electronics then transfer torque from one clutch to the other. This can make shifts very quick and reduce the efficiency losses associated with a traditional torque converter.

Kégresse’s idea predates the modern era by decades. One early production example was the Easidrive system, developed by Smiths Industries and Rootes and offered on the 1961 Hillman Minx Series IIIC. Porsche later popularized the technology in modern road and racing applications under the PDK name.