Gearbox structure

The utility model relates to a gearbox structure, which belongs to the field of automobile transmission speed control systems, and comprises a first shaft, a second shaft, a third shaft and a fourth shaft, the second shaft is sleeved with a high-gear normally engaged gear, a gear and a reverse gear, and the output end of the second shaft is in transmission connection with a planetary auxiliary box; and the low-gear normally engaged gear, the high-gear normally engaged gear, the gear-position gear and the reverse-gear gear are all in transmission connection with the intermediate shaft through gears. Due to the fact that the low-gear normally-meshed gear and the high-gear normally-meshed gear are arranged, the first shaft can selectively drive the low-gear normally-meshed gear or the high-gear normally-meshed gear to rotate, the middle shaft can be driven to rotate through the low-gear normally-meshed gear or the high-gear normally-meshed gear, and then the middle shaft can drive the reverse gear or the gear ge