At the beginning of the 1990s, Saab, a company that had long earned a reputation as a manufacturer with unconventional engineering thinking, offered buyers an unusual solution: the Sensonic manual transmission. Formally, it remained a "manual": the driver still shifted gears with a familiar lever. However, one important element was missing from the cabin: the clutch pedal. The driver had only the accelerator and brake at their disposal.
In those years, Saab was often called the "Swedish BMW." The company consistently focused on driving pleasure and, for that reason, was not afraid to introduce technologies that departed from generally accepted conventions. Sensonic became one of the clearest examples of this approach.
The context for the appearance of this gearbox was quite clear. The end of the 20th century was a time when major cities around the world were faced with chronic traffic congestion. Driving in traffic jams with a classic manual transmission irritated many people: constant use of the clutch pedal combined with the gear lever turned every trip into a tiring process.
At the same time, the automatic transmissions of those years also had serious limitations. For drivers who valued performance, they often proved too slow. In situations where rapid acceleration was required, for example during overtaking, the automatic would often begin leisurely working through the gears instead of delivering the sharp kick-down that was expected. This problem was especially acute in combination with turbocharged engines, and Saab was best known precisely for such powerplants.
How Sensonic Was Designed
Saab engineers decided to preserve the advantages of a manual gearbox while eliminating its most tiring operation: clutch work. Thus the Sensonic transmission appeared, in which clutch engagement and disengagement were handled by a hydraulic actuator controlled by electronics. A sensor was built into the gearshift lever itself: as soon as the driver merely applied force to the knob, the system automatically disengaged the clutch.
This gearbox was installed on the turbocharged Saab 900 NG Turbo. Moreover, the proprietary Trionic engine management system was integrated with Sensonic and taught to adjust throttle operation at the moment the clutch was disengaged. Thanks to this combination, the car pulled away smoothly and accelerated confidently, while the gear-changing process felt easy and intuitive. Many drivers adapted to the new setup quite quickly and spoke of it sympathetically.
An Idea Ahead of Its Time
However, by the end of the 1990s, the situation had changed. Saab replaced the 900 with the 9-3 and at the same time abandoned its original transmission. Over time, Sensonic revealed significant drawbacks.
One of the problems lay in the system's sensitivity. Drivers would sometimes accidentally touch the gearshift lever, and the gearbox reacted instantly by disengaging the clutch. At such moments, people became confused and sometimes were even frightened by the car's unexpected behavior. Starting on an incline was another challenge: such a maneuver in a Sensonic-equipped car required skill and did not always go smoothly.
The key factor, however, was reliability. The gearbox proved difficult to service, and specialists at many authorized service stations simply did not have sufficient experience working with this transmission and were reluctant to take on its repair.
As a result, Saab cars with the Sensonic gearbox are very rare today. Virtually all owners of such cars eventually replaced the unusual transmission with a classic manual gearbox.
Was It the First?
Strictly speaking, the very idea of a manual gearbox without a clutch pedal was not unique. Long before Saab, in West Germany, starting in the 1960s, the Saxomat transmission was offered, operating on a similar principle but using an electropneumatic actuator. In those same years, in the USSR, a version of the Zaporozhets was developed for disabled drivers with a gearbox using a ferromagnetic clutch. All of these solutions remained low-volume experiments.
Nevertheless, it was the Swedish company that first dared to offer such a transmission to a wide circle of ordinary car owners. Yes, this step proved premature and involved technical compromises. But it was Sensonic that allowed Saab to write yet another unusual page in the history of automotive engineering.