A transmission is connectable to an input member and includes an output transfer gear, first and second transmission input shaft members, first and second countershaft members, a plurality of co-planar gear sets, and a plurality of torque transmitting devices. The torque transmitting devices include a plurality of synchronizer assemblies and a dual clutch assembly. The transmission is operable to provide at least one reverse speed ratio and a plurality of forward speed ratios between the input member and the output member.

A planetary gear train is provided. The gear train includes input and output shafts and first to fourth planetary gear sets that respectively have first to third, fourth to sixth, seventh to ninth, and tenth to twelfth elements. A first shaft is connected with the first and fourth elements and selectively connected with the input shaft, a second shaft is connected with the sixth element and selectively connected with the input shaft, a third shaft is connected with the eighth element and the output shaft, a fourth shaft is connected with the second, fifth, and ninth elements, and a fifth shaft is connected with the third and eleventh elements. A plurality of shafts are each selectively connected to the transmission housing and connected to an element of the third and fourth planetary gear sets that is not connected with any of the first to seventh shafts.

An automatic transmission includes first shaft, second shaft, four planetary gear sets, and six shift elements for forming different gear ratios between the first and second shafts. The first, third and fourth planetary gear sets are negative planetary gear sets and the second planetary gear set is a positive planetary gear set. The planetary gear carriers of the first, second, and fourth planetary gear sets are connected and form the first shaft. The planetary gear carrier of the third planetary gear set forms the second shaft. First shift element is between a third shaft and the housing; second shift element is between a fourth shaft and the housing; third shift element is between second and eighth rotatable shafts; fourth shift element is between fourth and sixth rotatable shafts; fifth shift element is between fifth and seventh rotatable shafts; and sixth shift element is between sixth and the seventh rotatable shafts.

A planetary gear train of an automatic transmission for a vehicle may include: an input shaft receiving torque of an engine; an output shaft outputting torque; a direction changer disposed on an input shaft side and transmitting the torque of the engine to the input shaft with or without change of rotation direction, or disposed on an output shaft side and outputting the torque of the output shaft with or without change of rotation direction; a first planetary gear set including first, second and third rotation elements; a compound planetary gear set including fourth, fifth, sixth, and seventh rotation elements by combining second and third planetary gear sets; a fourth planetary gear set including eighth, ninth, and tenth rotation elements.

A planetary gear train of an automatic transmission for a vehicle is disclosed and may include: an input shaft receiving torque of an engine; an output shaft outputting torque; a first, second, third and fourth planetary gear set, each having three rotation elements, together first-twelfth rotation elements; a first shaft fixedly connected to a second rotation element and selectively connected to the input shaft; a second shaft fixedly connected to a fourth rotation element and selectively connected to the input shaft; a third shaft fixedly connected to an eighth rotation element and a twelfth rotation element, and fixedly connected to the output shaft; a fourth shaft fixedly connected to a first rotation element, a fifth rotation element, and a ninth rotation element; a fifth shaft connected to a sixth rotation element and an eleventh rotation element; and a plurality of shafts selectively connected to a transmission housing.

A multi-stage transmission for a vehicle includes: a first planetary gear set and a second planetary gear set each including three rotating elements; a compound planetary gear set including four rotating elements; and eight rotation shafts connected to the rotating elements of the planetary gear sets.

A planetary gear train is provided. The gear train includes input and output shafts and first to fourth planetary gear sets that respectively have first to third, fourth to sixth, seventh to ninth, and tenth to twelfth elements. A first shaft is connected with the first and fourth elements and selectively connected with the input shaft, a second shaft is connected with the sixth element and selectively connected with the input shaft, a third shaft is connected with the eighth element and the output shaft, a fourth shaft is connected with the second, fifth, and ninth elements, and a fifth shaft is connected with the third and eleventh elements. A plurality of shafts are each selectively connected to the transmission housing and connected to an element of the third and fourth planetary gear sets that is not connected with any of the first to seventh shafts.

A center support (11c) having a sidewall part (111c) extending from an internal circumferential surface of a transmission case (11) toward a radial inner side of the transmission case (11); and a cylindrical part (112c) axially extending from an internal circumferential portion of the sidewall part (111c) is formed between a first drive gear (26) with a small diameter and a second drive gear (28) with a large diameter. The first drive gear (26) is turnably supported by a first bearing (31) on an internal circumferential surface of the cylindrical part (112c) of the center support (11c), and the second drive gear (28) is turnably supported by a second bearing (32) on an external circumferential surface of the cylindrical part (112c).

A transmission for a vehicle capable is provided to improve fuel efficiency through multiple gear shift stages and enhance power performance of an engine. By combining first and second planetary gear sets, a compound planetary gear set, and multiple frictional elements selectively connecting rotary components of the three planetary gear sets via a corresponding shaft, the transmission provides eleven forward gear stages and three reverse gear stages. In particular, a first rotary element of the first planetary gear is fixedly connected to a transmission case, a second rotary element of the first planetary gear is fixedly connected to a second rotary element of the second planetary gear, and a third rotary element of the first planetary gear device is selectively connected to a first rotary element of the compound planetary gear set and a fourth rotary element of the compound planetary gear set.

A planetary gear train of an automatic transmission for a vehicle is disclosed. The planetary gear train may include: a first planetary gear set including first, second, and third rotation elements; a second planetary gear set including fourth, fifth, and sixth rotation elements; a third planetary gear set including seventh, eighth, and ninth rotation elements; a fourth planetary gear set including tenth, eleventh, and twelfth rotation elements; an input shaft, the first, second, and third planetary gear sets being disposed at a radial outer of the input shaft; and an output shaft disposed in parallel with the input shaft, the fourth planetary gear set being disposed at a radial outer of the outer shaft.