Four-wheel drive automatic transmission

Claim 1

A four-wheel drive automatic transmission comprising: an automatic transmission having: a transmission case including a first end face; a transmission mechanism mounted in the transmission case, and an automatic transmission hydraulic control unit including: a transmission valve body secured to the bottom surface of the transmission case; and a first flow passage for working hydraulic fluid for operating said transmission mechanism, said first flow passage cast in and extending through a wall of said transmission case and opening to the exterior of said transmission case at said first end face, said first flow passage defining a path, inside said transmission case, for fluid communication between said transmission valve body and said first end face; a four-wheel drive transfer unit having: a transfer case including a second end face directly abutting said first end face of the transmission case to define a planar interface therebetween, a transfer mechanism mounted in the transfer case, and, a transfer hydraulic control unit, including: a transfer valve body secured to the bottom surface of the transfer case; a second flow passage, inside said transfer case, for the working hydraulic fluid supplied to said transfer valve body, said second flow passage cast in and extending through a wall of said transfer case and opening to the exterior of said transfer case at said second end face where said second flow passage connects with said first flow passage to establish a continuous flow path within said housings for fluid communication between said transmission valve body and said transfer valve body; and oil seal means between said end faces and surrounding the connected flow passages.