Has the prototype been verified? Rapid prototyping is also possible. Then talk to the transmission (gearbox) manufacturer and directly talk to the general manager or technical manager. If they are interested, it will be easy. It is indirect to find an automobile manufacturer or other organization, and the transmission (gearbox) manufacturer also has autonomy and right to speak in the automobile factory (main engine factory). Find more companies, including foreign manufacturers, and you will succeed.
(Unfortunately, my "Car Height Warning Device", patent number: 20 12206 10028.3, has also been dormant for more than two years. . . )