Mechanical transmission system, associated powertrain and associated vehicle

A mechanical transmission system for a powertrain of a vehicle, the mechanical transmission system comprising:

• an automated gearbox comprising different gears, the gears being configured to be switched between different configurations, in each configuration a gear associated to the given configuration is configured to connect a primary part of the powertrain to a secondary part of the powertrain with a transmission coefficient associated;
• a pressurized air system adapted to switch the gears from one configuration to another configuration;
• and
• a controller configured to command the switching of the gears between the different configurations according to gear selection rules, the gear selection rules evolving between normal selection rules when a pressure of the pressurized air system is above a first threshold, and safety selection rules when the pressure of the pressurized air system is below the first threshold, the safety selection rules imposing a waiting time between two successive switching of the gears.