Eight-gear transmission for heavy duty vehicle

The utility model discloses an eight-gear transmission for a heavy duty vehicle and belongs to the field of motor vehicle transmissions. The eight-gear transmission comprises a four-forward-gear main transmission, a two-gear auxiliary transmission, a synchronizer, a casing, a positioning pin, a conical bearing, a front end cover, a rear cover, an input shaft, a middle shaft assembly and a filtering system. The four-forward-gear main transmission and the two-gear auxiliary transmission forms a combined transmission, the casing comprises a main casing, a front casing and a rear casing, the input shaft horizontally penetrates through the casing through the bearing, the filtering system comprises an oil pump, a secondary oil filter, an oil sump, a primary oil filter, a sealing ring, a cover, a plug screw and a bolt, and the filtering system is communicated with an oil path of the transmission. The eight-gear transmission is compact in structure, multiple in gears and small in gear ranges, can help a whole vehicle