The Way a Non Syncro Manual Transmission Works

   The earliest form of the manual transmission is thought to have been invented by Louis René Panhard and Emile Levassor in the late 19th century. This type of transmission offered multiple gear ratios and, in most cases, reverse. The gears were engaged by sliding them, or dog clutches, on their shafts hence the term shifting gears, which required a lot of careful timing and throttle manipulation when shifting, so that the gears would be spinning at roughly the same speed when engaged, otherwise, the teeth would refuse to mesh.

  When upshifting, the speed of the gear driven by the engine had to drop to match the speed of the next gear, as this happened naturally when the clutch was depressed or disengaged, it was just a matter of skill and experience to hear and feel when the gears managed to mesh. However, when downshifting, the gear driven by the engine had to be sped up to mesh with the output gear, requiring letting the clutch up, engagement, for the engine to speed up the gears. Double clutching, that is, shifting once to neutral to speed up the gears and again to the lower gear, is sometimes needed. In fact, such a manual transmission is often easier to shift without using the clutch at all. When using this method, the driver has to time the shift with relative precision to avoid grinding the gears. The clutch, in these cases, is only used for starting from a standstill. This procedure is common in racing vehicles and most production motorcycles.

  Similarly, most modern motorcycles still use an unsynchronized manual transmission, as synchronizers are generally not necessary or desirable. Their low gear inertias and higher strengths mean that forcing the gears to alter speed is not damaging, and the selector method on modern motorcycles, pedal operated is not conducive to having the long shift time of a synchronized manual transmission. Because of this, it is still necessary to synchronize gear speeds by blipping the throttle when shifting into a lower gear on a motorcycle.

  Even though an automotive manual transmission is now almost universally synchronised, a dedicated racing manual transmission is usually not, such a manual transmission is colloquially referred to as a, crashbox. Non synchronized designs are used for several reasons. The friction material, such as brass, in synchronizers is more prone to wear and breakage than gears, which are forged steel, and the simplicity of the mechanism improves reliability and reduces cost. In addition, the process of shifting a synchromesh manual transmission is slower than that of shifting a non synchromesh manual transmission. For racing of a production based manual transmission, sometimes half the teeth, or dogs, on the synchros are removed to speed the shifting process, at the expense of greater wear.