Planetary gear train of an automatic transmission for a vehicle

A planetary gear train of an automatic transmission for a vehicle, the planetary gear train comprising:

• an input shaft receiving torque of an engine;
• an output shaft outputting an output torque;
• a first planetary gear set including a first rotation element, a second rotation element, and a third rotation element;
• a second planetary gear set including a fourth rotation element, a fifth rotation element, and a sixth rotation element;
• a third planetary gear set including a seventh rotation element, an eighth rotation element, and a ninth rotation element;
• a fourth planetary gear set including a tenth rotation element, an eleventh rotation element, and a twelfth rotation element;
• a first shaft connected to the first rotation element;
• a second shaft connecting the second rotation element to the fourth rotation element and the seventh rotation element and connected to the input shaft;
• a third shaft connecting the third rotation element to the eleventh rotation element;
• a fourth shaft connecting the fifth rotation element to the twelfth rotation element and connected to the output shaft;
• a fifth shaft connected to the sixth rotation element and selectively connected to the third shaft;
• a sixth shaft connected to the eighth rotation element;
• a seventh shaft connected to the ninth rotation element;
• and
• an eighth shaft connected to the tenth rotation element, selectively connected to the sixth shaft, and selectively connected to the seventh shaft.