First introduced in the E36 M3 in 1997, BMW’s sequential manual gearbox, or SMG, is a direct descendant of Formula 1 technology. The SMG allows the driver to select either an automatic or manual mode. This differs somewhat from BMW’s Steptronic gearbox, which also has manumatic shifting. The Steptronic gearbox is akin to an automatic transmission with a manual mode, while the SMG is more of a manual transmission with an automatic mode.
The SMG I was the first car to be mass produced. The gearbox sold very well in the M3 and a revamped edition was produced for the E46 M3 in 2001. Dubbed the SMG II, this six speed gearbox for the restyled M3 increased reliability and provided quicker shifts. Also introduced was the Drivelogic system, which provides adjustable settings for different shift modes. Drivers can place the car in sport mode where shift times are decreased, throttle response is increased and the car is ready for the track. There is also a launch control mode, which automatically sets the car up for an optimal standing start. For daily driving, the car can be placed in a more civil mode with softer shifts and more economical driving.
BMW introduced a new gearbox, the SMG III, for the E60 M5 and E63/E64 M6 in 2005. The SMG III was specifically designed to be mated with those cars' V10 engines and provide maximum performance. The SMG III features seven forward gears, up from the previous six. The Drivelogic system and launch control from the previous version was carried over and the SMG III introduced the “M Button”, a steering wheel mounted button that would put the car into race mode and automatically set the engine and gearbox to their most hardcore settings. In 2008, the SMG was replaced in the E90 M3 with the M-DCT, a dual clutch transmission that offers similar functionality and increased performance.
The SMG eliminates the need for a clutch pedal in a manual transmission, and a torque converter in an automatic transmission. Instead, there is a standard gearbox with a hydraulically-operated clutch and console and steering wheel mounted shifters. While in manual mode, the driver changes gears using either the console mounted shifter, pulling back for upshifts and forward for downshifts, or the steering wheel mounted paddles, using the right paddle for upshifts and the left paddle for downshifts. The clutch is engaged by computer electronics and a hydraulic system when a new gear is selected. This results in ultra fast shifts, around 80 milliseconds; much faster than a true manual transmission.