Synchronizers (Synchros)

"Synchros" are synchronizers inside the transmission. These are the actual parts that move when you move your gear shift from side to side and back and forth. Their job is to connect the gears of the transmission to the shafts that they ride on and lock them together. This must be done at a gradual rate or the gears will grind. The synchronizer drives a cone shaped metal piece against the gear and starts the gear spinning. It accelerates it to the speed of the output shaft. When the gear reaches the speed of the output shaft, the synchro meshes completely with both of them and directs drive through its splines from the gear to the output shaft or vice versa. Some cars allow you to shift without pressing the clutch. If you shift gears slowly, the synchro will do the entire job and you never have to press the clutch. This comes in handy if you've sprained your left ankle.