Diesel rail cars in Japan have played a major role in transportation on mountainous lines. However, their efficiency of current transmission is low and their running speed is slow, because they run by hydraulic stage of current transmission. The authors built a new transmission system equipped with two direct stages of claw clutch. The transmission was tested in RTRI, JR. Recently, they built two transmission systems improved upon a previous transmission with reference to the test result. The transmissions were installed in a standard diesel railcar of JR. and tested on a mountainous main line of JR after a test in RTRI, JR. The test result was satisfactory. The running efficiency of diesel rail cars will be improved greatly thyough the adoption of this transmission.
