Speed reducer and vehicle

The invention relates to the technical field of speed reducers, in particular to a speed reducer and a vehicle, the speed reducer comprises a shell, an oil storage part and a sliding part, an oil storage cavity is formed in the oil storage part, the shell is provided with a transmission cavity, the oil storage part is arranged at the bottom of the transmission cavity, the oil storage cavity communicates with the transmission cavity, and the sliding part is slidably arranged in the oil storage cavity; the volume of the oil storage cavity is adjusted. According to the speed reducer and the vehicle provided by the invention, the oil quantity in the transmission cavity of the speed reducer is adjusted, so that the speed reducer can adjust the oil quantity in the transmission cavity according to the rotating speed of the rotating part, and on the premise that the rotating part is always kept in a good lubricating state, the situation that the oil quantity in the transmission cavity is too much is effectively avoid