Gearbox comprising a means for locking an output shaft and vehicle comprising such a gearbox

The gearbox has a rotation blocking mechanism (2) selectively co-operating with an output shaft of a casing, where the casing comprises an input shaft and gears. Each gear (41) is formed by a fixed pinion carried by one of the shafts, and an idle pinion carried by the other shaft. Jaw clutching units of each pinion comprise a jaw clutch axially movable under the action of forks (5a, 5b) moved by an actuator common to the jaw clutching units. The blocking mechanism has a control unit formed by the actuator, where the actuator comprises a cylinder (3) rotatably moved by an electric motor (4).