Most keen drivers tend to prefer manual transmissions. Meanwhile, standardised fuel efficiency/emissions tests increasingly favour automatic tranmsissions with 7, 8 or even 9 ratios that can be almost perfectly tailored to the requirements of the test to achieve a lower CO2 rating.
Hence manual gearboxes, where anything more than 6 forward gears requires a fourth shift gate which is usually deemed too much for drivers to cope with, are becoming a threatened species in some vehicle segments.
As can be seen in patent drawings first uncovered on BMW fansite Bimmerpost, the Munich carmaker has devised a solution that makes it virtually impossible for drivers to inadvertently shift from, say, 7th into 2nd gear. According to the patent design, the shift gates are surrounded by a magnetorheologic or electrorheologic fluid similar to what is used in some 'active' suspension dampers. Relying on various sensors, a computerized shifting module calculates which gears are allowable and which gears are wrong to select, given the driving situation. To prevent an improper shift, a magnetic field or electric voltage is applied to change the viscosity of the fluid, which will physically block the engaging of certain gears.
The patent specifically mentions two applications for the new technology; a conventional manual gearbox, and an automated manual 'shift by wire' system.