Several famous marques used A-type overdrives, including Jaguar, Aston Martin, Ferrari, Austin-Healey, Jensen, Bristol, AC, Armstrong Siddeley and Triumph's TR sports car range, from the TR2 through to the end of the 1972 model year of the TR6. The first unit to be created was the A-type overdrive, which was fitted to many sports cars during the 1950s, and into the late 1960s. The first production vehicle to feature the Laycock system was the 1948 Standard Vanguard Saloon. Another British company, the former aircraft builder Fairey, built a successful all-mechanical unit for the Land Rover, which is still in production in America today. De Normanville overdrives were found in vehicles manufactured by Standard-Triumph, who were first, followed by Ford, BMC and British Leyland, Jaguar, Rootes Group and Volvo to name only a few. The system was devised by Captain Edgar J de Normanville (1882–1968), and made by Laycock through a chance meeting with a Laycock Products Engineer. If you have the trans apart at the same time, you can use the output shaft as a dummy.The vast majority of overdrives in European cars were invented and developed by a man called de Normanville and manufactured by an English company called Laycock Engineering (later GKN Laycock), at its Little London Road site in Sheffield. If you do strip it down, you have to line up the splines on the planetary and the overrunning clutch to get it to re-engage the output shaft. With yours sitting in the garage, thats not an option, so you may need to pull the pan off and pry the cone clutch towards the front of the unit to get it to release from the output shaft of the trans. One tip- they can be a bit of a bugger to get off the output shaft if you can't engage and run the od unit on the car.

I'd bet if you ordered 240 bits, they'd fit fine, and probably be better quality than repro Brit stuff. They used them into the 90's, although the last few years were a larger unit.

If you decide to get into it, I'd bet most parts are available through Volvo. There can be bearing troubles, but you should be able to hear them by giving the output shaft a spin after pulling it off the trans. Volvo upsized the oring grooves and orings in the pistons a couple of times over the years. Really, the only thing on a J type that ever gives trouble is the orings on the two actuating pistons- at least at that type of mileage.

J type laycock overdrive