A transmission at least comprising: a first shaft ; a second shaft ; a third shaft ; and a fourth shaft ; wherein the first, second, third, and fourth shafts are parallel to each other; wherein the first shaft includes a first gear and a second gear , the first gear coupling to the first shaft , the second gear coupling to or idling around the first shaft when a first clutch is switched; wherein the second shaft includes a third gear and a fourth gear , the third gear meshing with the first gear and coupling to the second shaft , the fourth gear coupling to or idling around the second shaft when a second clutch is switched; wherein the third shaft includes a sixth gear and a seventh gear , the sixth gear meshing with the first gear and coupling to the third shaft , the seventh gear coupling to or idling around the third shaft when a fourth clutch is switched; and wherein the fourth shaft includes a ninth gear , the ninth gear meshing with the second gear , the fourth gear , and the seventh gear , and coupling to the fourth shaft , characterized in that the transmission further comprises: a fifth shaft that is parallel to the fourth shaft ; wherein the fourth shaft includes an eleventh gear and a twelfth gear , the eleventh gear coupling to the fourth shaft , the twelfth gear coupling to or idling around the fourth shaft when a sixth clutch is switched; and wherein the fifth shaft includes a fourteenth gear and an eighteenth gear , the fourteenth gear meshing with the twelfth gear and coupling to the fifth shaft , the eighteenth gear meshing with the eleventh gear , and coupling to or idling around the fifth shaft when an eighth clutch is switched. a first shaft ; a second shaft ; a third shaft ; and a fourth shaft ; wherein the first, second, third, and fourth shafts are parallel to each other; wherein the first shaft includes a first gear and a second gear , the first gear coupling to the first shaft , the second gear coupling to or idling around the first shaft when a first clutch is switched; wherein the second shaft includes a third gear and a fourth gear , the third gear meshing with the first gear and coupling to the second shaft , the fourth gear coupling to or idling around the second shaft when a second clutch is switched; wherein the third shaft includes a sixth gear and a seventh gear , the sixth gear meshing with the first gear and coupling to the third shaft , the seventh gear coupling to or idling around the third shaft when a fourth clutch is switched; and wherein the fourth shaft includes a ninth gear , the ninth gear meshing with the second gear , the fourth gear , and the seventh gear , and coupling to the fourth shaft , characterized in that the transmission further comprises: a fifth shaft that is parallel to the fourth shaft ; wherein the fourth shaft includes an eleventh gear and a twelfth gear , the eleventh gear coupling to the fourth shaft , the twelfth gear coupling to or idling around the fourth shaft when a sixth clutch is switched; and wherein the fifth shaft includes a fourteenth gear and an eighteenth gear , the fourteenth gear meshing with the twelfth gear and coupling to the fifth shaft , the eighteenth gear meshing with the eleventh gear , and coupling to or idling around the fifth shaft when an eighth clutch is switched. a fifth shaft that is parallel to the fourth shaft ; wherein the fourth shaft includes an eleventh gear and a twelfth gear , the eleventh gear coupling to the fourth shaft , the twelfth gear coupling to or idling around the fourth shaft when a sixth clutch is switched; and wherein the fifth shaft includes a fourteenth gear and an eighteenth gear , the fourteenth gear meshing with the twelfth gear and coupling to the fifth shaft , the eighteenth gear meshing with the eleventh gear , and coupling to or idling around the fifth shaft when an eighth clutch is switched. <EOS>