Gearshift
In dual-shaft transmissions, shifting into different gears takes place by means of an appropriate shifting clutch agent. In this case one differentiates between:
Positively-engaged shifting clutch agents and
Friction shifting clutch agents
In manual transmissions, shifting gears takes place over gearshift rods. By displacing sleeves, they establish a positively-engaged link between gear wheel and shaft. A speed synchronization of shaft and gear wheel is required. The so called non-synchronized transmissions were used for a long time, where the speed equalization was achieved by double declutching on the part of the driver. The correct handling of non-synchronized transmissions requires a certain skill, the result being that they are only occasionally used in trucks today. In order to achieve convenient operation at high shift speeds, low noise and low wear, the forward gears of stepped transmissions are synchronized by adherently ensuring the speed equality of the rotating parts that have to be engaged during gear shifts. The figure above shows locking synchronization.