Multi-stage gearbox

A multi step transmission of a planetary design for an automatic transmission of a motor vehicle, the multi step transmission comprising:

• a drive shaft (1);
• an output shaft (2);
• first, second, third and fourth planetary gear sets (P1, P2, P3, P4) disposed in a transmission housing (G), each of the first, the second, the third, and the fourth planetary gear sets (P1, P2, P3, P4) comprising a sun gear, a carrier and a ring gear;
• a third rotatable shaft (3), a fourth rotatable shaft (4), a fifth rotatable shaft (5), a sixth rotatable shaft (6), a seventh rotatable shaft (8), and an eighth rotatable shaft (9);
• at least six shift elements (03, 05, 13, 16, 18, 49) comprising a first brake (03), a second brake (05), a first clutch (13), a second clutch (16), a third clutch (18), and a fourth clutch (49) whose selected engagement produces different transmission ratios between the drive shaft (1) and the output shaft (2) such that nine forward gears and one reverse gear can be achieved;
• the first and the second planetary gear sets (P1, P2) form a shiftable front-mounted gear set and the third and the fourth planetary gear sets (P3, P4) form a main gear set;
• wherein the carriers of the first and the second planetary gear sets (P1, P2) are coupled together via the fourth shaft (4) which is connected to the sun gear of the third planetary gear set (P3);
• the ring gear of the first planetary gear set (P1) is coupled to the sun gear of the second planetary gear set (P2) via the seventh rotatable shaft (8), and the seventh rotatable shaft (8) is connectable to the drive shaft (1) via the third clutch (18);
• the sun gear of the first planetary gear set (P1) is connectable to the housing (G) by the third shaft (3), via the first brake (03), and is connectable to the drive shaft (1), via the first clutch (13);
• the ring gear of the second planetary gear set (P2) is connectable to the housing (G) by the fifth shaft (5) via the second brake (05);
• the sun gear of the fourth planetary gear set (P4) is connected by a fixed ninth shaft (7) to the housing (G);
• the sixth shaft (6) is connected to the carrier of the third planetary gear set (P3) and is connectable to the drive shaft (1) via the second clutch (16);
• the eighth shaft (9) is connected to the ring gear of the fourth planetary gear set (P4) and is connectable to the fourth shaft (4) via the fourth clutch (49);
• and
• the output shaft (2) is connected to the ring gear of the third planetary gear set (P3) and to the carrier of the fourth planetary gear set (P4).