Multi-stage transmission for vehicles

A multi-stage transmission for vehicles comprising:

• an input shaft for receiving power from an engine;
• an output shaft for outputting the power;
• a first planetary gear device, a second planetary gear device, a third planetary gear device, and a fourth planetary gear device, each of the planetary gear devices having three rotary elements;
• a first rotary shaft connected to the input shaft;
• a second rotary shaft connected to a first rotary element of the first planetary gear device and to a first rotary element of the second planetary gear device;
• a third rotary shaft connected to a second rotary element of the first planetary gear device and to a third rotary element of the second planetary gear device;
• a fourth rotary shaft connected to a third rotary element of the first planetary gear device;
• a fifth rotary shaft connected to a second rotary element of the second planetary gear device and to a first rotary element of the third planetary gear device;
• a sixth rotary shaft connected to a second rotary element of the third planetary gear device and to a third rotary element of the fourth planetary gear device;
• a seventh rotary shaft connected to a first rotary element of the fourth planetary gear device;
• and
• an eighth rotary shaft connected to a third rotary element of the third planetary gear device, to a second rotary element of the fourth planetary gear device, and to the output shaft.