An automatic transmission has a reduced axial dimension and includes a mission case portion providing a mounting surface for a valve body. Forces generated by a hydraulic servo in operation of a brake are confined to the inside of a rear cover joined to the mission case. An extension protrudes from the rear cover and extends into the interior of the mission case with a multi-plate brake splined thereto. The force generated in operation of the brake is received by the cylinder as a reaction force. However, since the hydraulic servo cylinder and the extension are both integral with the rear case, the reaction force is confined to the interior of the rear cover without acting on the mission case.