From the late 1940s into the 1960s, three on the tree was the transmission that came as standard equipment for most passenger cars. Chevy, Ford, Hudson and Studebaker were offering a free wheeling overdrive from Borg Warner as an option, but the automatic transmission was gaining in popularity. In England (today we call it the UK), the Laycock de Normanville overdrive was backing up many 4-speed transmissions. The Laycock Overdrive Unit was first introduced in October 1948, when it was fitted to a Triumph roadster as an aftermarket accessory and in 1952, the overdrive was factory installed on the Jaguar MK VII. This Overdrive Unit was a result of a chance meeting between Ken Walker, production engineer at Laycock Engineering Limited, and Captain Edgar de Normanville, an American transmission designer.

The Borg Warner overdrive faded in the late 1960s, never to be seen again as a production option, and was replaced by the automatic transmission. An overdrive returned to an American vehicle in 1984 and continued to 1988 as an option on the Corvette. It was produced by Doug Nash with an RPO of MH5 and was referred to as the 4+3 transmission. GKN Industries of the UK continues to produces a version of the Laycock overdrive for Land Rover and Volvo.

The Laycock type is alive and well in the US and being produced by Gear Vendors of El Cajon, CA. Their upgraded version of the overdrive is backing up automatic and manual t...