OEM manual transmissions are fitted with a synchronizes for engagement from the factory. The advantage is they deliver smooth, reliable, and quiet operation, which is paramount for a street driven vehicle. Synchromesh transmissions operate using a collar that applies force to a cone-shaped clutch attached to the gear. The collar allows the shaft speed of the gearset and the input shaft to be matched or synched to the output shaft prior to the collar locking into place and initiating a shift.
In special circumstances such as professional track racing the disadvantage of synchromesh gearboxes in high-performance applications include slow upshifting at very high engine speeds—e.g. 9,000 rpm—and slow downshifting, as well as the need to fully use the clutch.
Below is an assembled shaft showing typical synchromesh components.