Patent ID: 7524258

Claim:
A vehicular automatic transmission comprising: a stationary cylindrical housing; a first planetary gear device accommodated in said stationary cylindrical housing and including a ring gear: a first set of frictional coupling elements accommodated in said stationary cylindrical housing; a generally disc-shaped pump housing fixed to said cylindrical housing, so as to close an axial open end of the stationary cylindrical housing, and including a cylindrical extending portion which extends into said stationary cylindrical housing from a radially outer portion of said pump housing in an axial direction of said pump housing and which includes a radially inner spline-fitting part; said first planetary gear device being disposed radially inwardly of said radially inner spline-fitting part; said first set of frictional coupling elements being disposed between said ring gear of said first planetary gear device and said radially inner spline-fitting part of said cylindrical extending portion, to selectively fix ring gear to said cylindrical extending portion; a first retainer ring fixed to an axial end portion of said radially inner spline-fitting part, which axial end portion is remote from said pump housing, said first retainer ring abutting said first set of frictional coupling elements, to limit an axial movement of said first set of frictional coupling elements; a first hub including a splined cylindrical portion having splined outer and inner circumferential surfaces, and further including an annular flange portion which extends from an axial end of said splined cylindrical portion radially inwardly of said splined cylindrical portion, said splined cylindrical portion being splined at its splined inner circumferential surface to an outer circumferential surface of said ring gear, and at its splined outer circumferential surface to radially inner portions of said first set of frictional coupling elements, so as to permit an axial movement and prevent a rotary movement of said first hub relative to said ring gear and said first set of frictional coupling elements; said ring gear having a first circumferential groove formed in said outer circumferential surface, and said splined cylindrical portion of said first hub having a second circumferential groove formed in said splined inner circumferential surface; and a second retainer ring being fitted in said first and second circumferential grooves, whereby said first set of frictional coupling elements and said first planetary gear device can be supported by said pump housing via said first and second retainer rings, at predetermined axial positions within said cylindrical extending portion of said pump housing, during assembling of the vehicular automatic transmission.