Planetary gear train of automatic transmission for vehicle

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

• an input shaft receiving an input torque;
• an output shaft outputting a shifted torque;
• a first planetary gear set having a first rotation element, a second rotation element, and a third rotation element;
• a second planetary gear set having a fourth rotation element, a fifth rotation element, and a sixth rotation element;
• a third planetary gear set having a seventh rotation element, an eighth rotation element, and a ninth rotation element;
• a fourth planetary gear set having a tenth rotation element, an eleventh rotation element, and a twelfth rotation element;
• a first shaft fixedly connected to the input shaft, the third rotation element, and the fifth rotation element;
• a second shaft fixedly connected to the ninth rotation element and the eleventh rotation element, and selectively connectable to the input shaft;
• a third shaft fixedly connected to the eighth rotation element, the twelfth rotation element, and the output shaft;
• a fourth shaft fixedly connected to the first rotation element;
• a fifth shaft fixedly connected to the second rotation element and the sixth rotation element;
• a sixth shaft fixedly connected to the tenth rotation element;
• and
• a plurality of shafts, each of which is selectively connectable to a transmission housing and fixedly connected to a rotation element of the first and second planetary gear sets which is not fixedly connected to the first to sixth shafts.