The Smiths Easidrive automatic transmission was first introduced by Rootes Motors in September 1959 in the UK and February 1960 in the U.S. It was offered as an option on the Series IIIA Hillman Minx and for the next three years on subsequent Minxes and other Rootes models such as the Singer Gazelle and Hillman Super Minx. It was the first fully automatic transmission available on a small car. Up until that point conventional automatics were available only on larger cars with 6 or 8 cylinder engines. The hydraulic clutches or converters in these automatic transmissions used up a great deal of energy which the smaller 4 cylinder engines didn't have to spare and adversely affected fuel economy and performance as a result. The much smaller cars of Europe produced sometimes less than half the horsepower of their American counterparts and fuel was much more expensive so these types of transmissions were not considered a viable option.
Enter the Smiths Easidrive. This transmission was originally developed by the Eaton Yale Company of the United States. The Eaton Yale Company was a manufacturer of conveyer systems and other industrial equipment such as fork lifts. They developed an electric clutch for use in industrial applications. Having found this clutch to be very successful they decided to develop the idea further into an automatic transmission. Once produced they could find no buyers for this new transmission with any of the U.S. automobile manufacturers.
Having failed to convince any of the American auto makers to purchase the Easidrive system they offered the technology to manufacturers in Europe. The Smiths Company of England liked what they saw and bought the rights to the system. They developed it further and shopped it around to different manufacturers and found a buyer in the Rootes Motors Company. Rootes was impressed by the fact that the transmission required very little power to operate and delivered gas mileage of only slightly less than a manual gearbox. It also did not affect performance in any significant way. I'm sure that Rootes felt that this would open up a huge new market for them, especially in the U.S., but this was not to be.
THE SMITHS EASIDRIVE TRANSMISSION
How it works: The actual gearbox is very similar to a manual gearbox. However that's where the similarity ends. Attached to the engine, on the end of the crankshaft, is a driving member (like a drum). Attached to the gearbox, on the input shaft, is a driven member, a smaller drum that fits inside the larger drum. Actually there are two driven members (smaller drums) one in front of the other. The front one is connected to the mainshaft and enables direct drive. The rear one drives the countershaft which in turn drives the main shaft through a set of constant mesh gears and a freewheel giving low gear and by a solenoid operated dog clutch which activates intermediate gear. In between each smaller drum and the larger driving drum that surrounds them is a small air gap that is filled with iron powder. While the car is in neutral these iron particles are tossed around inside this gap. When a gear is selected a stationary magnetic coil inside the bellhousing is energised. This causes the iron powder to form in little solid columns between the two members (one of the smaller drums, depending on which gear is selected, and the larger drum) creating a solid coupling between engine and gearbox. Reverse gear is obtained (I'm quoting the manual now) "by a sliding gear, splined to the mainshaft, which is manually engaged with the reverse gear train: moving this gear also disengages the freewheel." One positive to this system is that there is virtually no slippage thus very little loss of power unlike the torque converters used in conventional automatic transmissions.
The whole system is run by an under hood main control unit full of transisters and other electrical components like rectifiers and other things I don't quite understand. There is also a gear selector switch, a govenor which monitors road speed and throttle position, a gearshift solenoid for engaging the dog clutch inside the gearbox to engage intermediate gear and a throttle solenoid which will raise the engine revs when 2nd is selected from drive while throttle is in closed position. Sound complicated? Well I would imagine most mechanics on this side of the pond likely thought so and it didn't help things when problems were incurred and there was no Rootes dealership or service facility nearby.
Despite being quite complicated the system itself actually worked quite well. It was corrosion that was the system's greatest enemy, especially the earlier Stage 1 models which relied on many mechanical relays to do all the switching. Damp weather would corrode these switches and relays over time hindering their operation and giving the system a bad name in the motoring world and the public's eyes. By the time the newer improved Stage II system with its transistors came out the damage had already been done to the Easidrive's reputation and Rootes found them increasingly hard to get rid of.
With the introduction of the Series V Minx in 1963 Rootes replaced the troublesome Easidrive transmission with the Borg Warner 35 as the automatic option on it's range of cars. I'm not sure how many Easidrive Minxes remain in operation today but I personally know of four in North America including my own 1962 Series IIIC saloon.