A transmission unit for a vehicle, comprising: a plurality of input shafts , each of the input shafts having a shift driving gear thereon; a plurality of output shafts , wherein each of the output shafts has a shift driven gear configured to mesh with a corresponding shift driving gear; an output unit , wherein the output unit is configured to rotate with one of the output shafts at a different speed; an output synchronizer disposed on the one of the output shafts and configured to engage with the output unit to synchronize the output unit with the one of the output shafts; a reverse idler gear fitted over the one of the output shafts and configured to selectively engage with the output shaft; and a reverse output gear configured to mesh with the reverse idler gear , and further comprising a reverse synchronizer configured to synchronize the one of the output shafts with the reverse idler gear ; wherein the reverse idler gear and the output unit share the output unit synchronizer ; wherein the output unit synchronizer is configured as the reverse synchronizer, wherein the output unit comprises an output idler gear ; wherein the output idler gear is fitted over the one of the output shafts , further comprising a fixed output gear ; wherein the fixed output gear is fixed on another one of the output shafts, and wherein the fixed output gear is meshed with a shift driven gear of a main reducer; wherein the output unit is meshed with the shift driven gear of the main reducer; wherein the reverse output gear is a joint gear structure; wherein one gear part of the joint gear is meshed with the reverse idler gear ; and wherein the other gear part of the joint gear is meshed with the shift driven gear of the main reducer; further comprising: a generator gear fixed on one of the output shafts; a motor power shaft ; and a motor power shaft gear fixed on the motor power shaft and configured to rotate together with the generator gear . a plurality of input shafts , each of the input shafts having a shift driving gear thereon; a plurality of output shafts , wherein each of the output shafts has a shift driven gear configured to mesh with a corresponding shift driving gear; an output unit , wherein the output unit is configured to rotate with one of the output shafts at a different speed; an output synchronizer disposed on the one of the output shafts and configured to engage with the output unit to synchronize the output unit with the one of the output shafts; a reverse idler gear fitted over the one of the output shafts and configured to selectively engage with the output shaft; and a reverse output gear configured to mesh with the reverse idler gear , and further comprising a reverse synchronizer configured to synchronize the one of the output shafts with the reverse idler gear ; wherein the reverse idler gear and the output unit share the output unit synchronizer ; wherein the output unit synchronizer is configured as the reverse synchronizer, wherein the output unit comprises an output idler gear ; wherein the output idler gear is fitted over the one of the output shafts , further comprising a fixed output gear ; wherein the fixed output gear is fixed on another one of the output shafts, and wherein the fixed output gear is meshed with a shift driven gear of a main reducer; wherein the output unit is meshed with the shift driven gear of the main reducer; wherein the reverse output gear is a joint gear structure; wherein one gear part of the joint gear is meshed with the reverse idler gear ; and wherein the other gear part of the joint gear is meshed with the shift driven gear of the main reducer; further comprising: a generator gear fixed on one of the output shafts; a motor power shaft ; and a motor power shaft gear fixed on the motor power shaft and configured to rotate together with the generator gear . <EOS>