Self-Changing Gears was a British company, set up and owned equally by Walter Gordon Wilson and John Davenport Siddeley to develop and exploit the Wilson or pre-selector gearbox. Self-Changing Gears designed, built and licensed transmissions for various applications including light and heavy road vehicles, military, marine, and rail vehicles as well as motor racing cars.The original company Improved Gears Ltd was incorporated on 28 December 1928, and this later became Self-Changing Gears. The company moved a number of times in the early years, and in 1938 settled in premises at Lythalls Lane, Coventry. During the war, additional premises were used at Burbage, Leicestershire.