A vehicle transmission is adapted to transmit a power output from an engine unit to a wheel. The vehicle transmission includes a driving unit and a speed-changing unit. The driving unit includes a main box, a first driving mechanism disposed within the main box and adapted to be driven by the engine unit, and an output shaft driven by the first driving mechanism. The speed-changing unit includes an auxiliary box connected removably to the main box, a second driving mechanism disposed within the auxiliary box and driven by the output shaft, and an axle parallel to the output shaft and driven by the second driving mechanism. The axle is connected fixedly to the wheel, and extends into the auxiliary box.