Abstract: A gear shift mechanism in a transmission connecting a drive source to an output via a clutch. The gear shift mechanism acts on a plurality of gear pairs to select one thereof during a speed change when the clutch is disengaged. The gear shift mechanism has a hollow shaft which can be the input or output shaft of the transmission. One of the gears of the gear pairs are idly mounted on the hollow shaft and the other of the gears of the gear pairs are secured to the output shaft or a further shaft connected thereto. Alocating tube rotates with the hollow shaft and is slidable therein. The locating tube and hollow shaft have a plurality of angularly aligned radial holes and when one of the idler gears of the gear pairs is selected for engagement, the locating tube is displaced to align the radial holes therein with holes in the selected idler gear. Each of the radial holes slidably supports an engagement pin.