PURPOSE: To provide easy and quick removal and refilling of oil by connecting a transfer pipe to a variable flow type fluid coupling and its auxiliaries, communicating its lower end with an oil storage tank, and communicating the oil storage tank with the transfer pipe through an oil feed pump.

CONSTITUTION: A transfer pipe 14 is communicatively provided respectively with the downstream side of an oil cooler 10, the inside of the case of a variable flow type fluid coupling 6 and the discharge sides of respective pumps of an oil pump unit 9. The lower end of the transfer pipe 14 is communicated with an oil storage tank 16, and the oil storage tank 16 is communicated with an oil feed pipe 18 through a valve 22 and an feed pump 17. The oil feed pipe 18 is connected to the transfer pipe 14 through an oil feed valve 19. For removing oil in the variable flow type fluid coupling 6 and its auxiliaries, the transfer valve 13 and a discharge valve 15 are opened, and oil is dropped in the oil storage tank 16 through the transfer pipe 14. After the completion of inspection, the discharge valve 15 is closed, an oil feed valve 19 is opened to drive the oil feed pump 17, fill respective apparatuses with oil to their original conditions through the oil feed pipe 18 and the transfer pipe 14, and close the transport valve 13, thus returning to normal condition.