Patent ID: 7731624

Claim:
An automatic transmission comprising: two clutches that are disposed at positions that overlap in an axial direction and are different in a radial direction, wherein the two clutches each comprise: a clutch drum, a piston that structures a working oil chamber with a portion of the clutch drum used as a cylinder, a plurality of friction plates that engage the clutch drum, and a cancel oil chamber that is disposed on a back surface side of the piston and that cancels a centrifugal hydraulic pressure that acts on the working oil chamber, wherein: an inner spline is formed on the clutch drum of one clutch, among the two clutches, that is positioned on an outer diameter side; an outer spline is formed on the clutch drum of the other clutch, among the two clutches, that is positioned on an inner diameter side; the inner spline and the outer spline are engaged; and the clutch drums of the two clutches are integrally linked in the rotational direction and in the axial direction.