A drive assembly having an actuating piston for generating a thrust for engagement of a clutch unit. The assembly also has a bearing for transferring the engagement thrust and a pusher for discharging the engagement thrust onto the clutch unit. The actuating piston, the bearing and the pusher are assembled in succession on a transmission shaft carrying the clutch unit. A chamber is provided for supplying a fluid under pressure for generating a disengagement thrust acting on the actuating piston. At least one preloaded spring is provided that acts on the actuating piston so as to push it towards the clutch unit. The bearing for transferring the thrust is mounted with play directly on the transmission shaft. The pusher being disk-shaped and comprising a first face in lateral contact with the bearing and a second face in lateral contact with the clutch unit.