PURPOSE: To prevent an increase in oil agitating resistance of a rotating member easily by fitting a weir of prescribed height onto connecting parts of both casings of a transmission and a transfer, and disposing an opening of a drain oil passage in a drive mode switching element inside the transmission for lowering an oil level in stored oil on the transfer side.

CONSTITUTION: A weir 11a of prescribed height is fitted onto connecting parts of both casings of a transmission 42 and a transfer 43, and low pressure oil is fed into the transmission 42 through an opening 721 of a drain oil passage 72 in a drive mode switching element B. Therefore, oil is capable of being stored up to a height of the weir 11a in the transmission 42, and a suitable amount of oil is distributed and stored respectively in the bottom part of the respective casings of an automatic transmission A/T and the transfer 43. It is thus possible to prevent respective rotating members of the transfer 43 on the lowest level side from agitating oil excessively for prevention of oil temperature rise, oil deterioration and output loss, and eliminate additional pump for returning oil for prevention of excessive cost increase.