10-speed power train of automatic transmission

PURPOSE: A 10-speed power train of an automatic transmission improves power transmission performance by forming a gear shift stage with forward 10-speed and backward 1-speed. CONSTITUTION: A first ring gear (R1) is always connected to a transmission case. A first planetary carrier (PC1) is connected to an input shaft. A second line gear (S2) is selectively connected to a second ring gear through a second clutch. The second ring gear is selectively connected to a first line gear through the second clutch or connected to the input shaft through a fifth clutch (CL5). A third planetary carrier (PC3) is selectively connected to the input shaft through a fourth clutch. A fourth line gear is directly connected to the second line gear and a third ring gear. A fourth ring gear (R4) is directly connected to the third planetary carrier.