Control system for controlling an oil level in a gearbox of a vehicle, associated gearbox assembly and vehicle

A gearbox assembly comprising:

• a gearbox of a vehicle;
• and
• a control system for controlling an oil level in the gearbox, wherein the gearbox comprises a main shaft and a countershaft, a gear ratio of the gearbox being controlled by several forks, including a first fork and a second fork, the gearbox having a direct drive configuration, where traction power does not pass through the countershaft and where the first fork and the second fork are in the direct drive configuration that engages a direct drive gear selection of the gearbox, wherein the control system comprises:
• a supply line, which is connected to a pressurized upstream oil supply of the gearbox,
• a return line, which is connected to the supply line,
• a first valve and a second valve,
• wherein:
• the first valve is configured:
• to be controlled by the first fork of the gearbox, and
• to switch between an open position and a closed position, according to a position of the first fork,
• the second valve is configured:
• to be controlled by the second fork of the gearbox, the second fork being different from the first fork, and
• to switch between an open position and a closed position, according to a position of the second fork,
• a first end of the return line is connected to the supply line through the first valve and the second valve, the first and second valves being arranged in serial, the first and second valves being both in the open position when the first and second forks are together in the direct drive configuration that engages the direct drive gear selection of the gearbox, so that the return line is pressurized when both valves are open and when the supply line is pressurized,
• the control system comprises a flow control unit, which is connected to a second end of the return line and which is configured to lower the oil level in an oil sump of the gearbox when the return line is pressurized.