Overload vehicle gearbox

The invention discloses an overload vehicle gearbox, and belongs to the field of gearboxes. The overload vehicle gearbox comprises an input shaft, an odd-gear transmission shaft, an even-gear transmission shaft and an output shaft. An input gear is arranged on the input shaft, a transmission gear A and an odd-gear gear set are arranged on the odd-gear transmission shaft, the input gear is engagedwith the transmission gear A and a transmission gear B, and the transmission gear B and an even-gear gear set are arranged on the even-gear transmission shaft. A driven gear set corresponding to the odd-gear gear set and the even-gear gear set is arranged on the output shaft, and the odd-gear transmission shaft and the even-gear transmission shaft are provided with a first one-way clutch and a second one-way clutch correspondingly. The clutches are not disconnected firstly during gear shifting, running is switched to the high gear under the condition that running continues at the low gear to maintain the advancing spe