Abstract: A six-speed powertrain of an automatic transmission is formed by combining three simple planetary gear sets, and an output element is realized as a single element without combination with a clutch. Therefore, because a torque load of a respective clutch is reduced, durability may be enhanced and a length of the transmission may be minimized.

Abstract: Six forward speeds and one reverse speed may be realized with minimized length and weight of the transmission by employing two single pinion planetary gear sets and a double pinion planetary gear set. One planetary gear of the double pinion planetary gear set is interconnected with an adjacent second planetary gear of the second single pinion planetary gear set by a common planet carrier such that they may rotate independently, and at the same time, at least two ring gears are integrated so as to enhance strength in the axial direction.

Abstract: A variable compound planetary gearset forms five operational elements by having its single and double pinion planetary gearsets be interconnected by a shared planet carrier. The variable compound planetary gearset forms six forward speeds and one reverse speeds by receiving input torque through two input routes fixedly or variably connected to a simple planetary gearset and one input route variably connected to an input shaft.

Abstract: A multiple speed automatic transmission having eight forward speeds and one reverse speed is realized by combining two simple planetary gear sets and one compound planetary gear set by five clutches and two brakes. Power is delivered efficiently and fuel consumption is enhanced due to the increased number of speeds of the automatic transmission. Step ratios of the eight forward speeds can harmonized so as to gradually decrease from the lower gear to the higher gear, thus shift-feel is be enhanced. Additionally, hill climbing ability in the reverse speed is also enhanced by increasing the speed ratio of the reverse speed.