A gear including a pinion being integral with a rotatably mounted shaft in a support by a cleavable element arranged to disengage the pinion from the shaft in case of an overcouple between the pinion and the shaft is disclosed. A guiding bearing, pending between the pinion and the shaft, is arranged to rotatably guide the pinion around the shaft, in case of a disengagement of the pinion from the shaft. In a turbomachine, a gear box including such a gear allows the driving of auxiliary machines in case of a breakdown of a shaft in the gear box.