The invention discloses a special transmission box body. The special transmission box body comprises a motor pulley, a motor belt, a main shaft pulley, a lower shaft belt, upper bearing seat mountingsubstrates, upper and lower shaft bearing seat assemblies, a tension wheel assembly, a lower shaft pulley, a lower shaft, a support arm, an upper shaft, a transmission box body assembly, a transmission box body, 6003 bearings and 6003 shaft sleeves. The special transmission box body is characterized in that the transmission box body assembly is installed on upper and lower bearing mounting substrates behind the support arm, and the shaft sleeve is pressed into the bearing; the upper shaft sequentially penetrates through an upper shaft bearing hole on the transmission box assembly, the main shaft pulley, the main shaft belt, the upper and lower shaft bearing assembly of the transmission box assembly, and the upper and lower shaft bearing assembly of the support arm; the main shaft pulley isfastened on the upper shaft; the lower shaft sequentially penetrates through a lower shaft bearing hole in front of the transmission box assembly, the lower shaft pulley, the lower shaft belt, the upper and lower shaft bearing block assembly of the transmission box assembly, and the upper and lower shaft bearing block assembly of the support arm; and the tension wheel assembly is installed insidethe transmission box body assembly.