Disclosed are a bidirectional overrunning clutch and a two-speed transmission. The bidirectional overrunning clutch comprises input teeth (2), fixed teeth (1), a transmission assembly and an output member, wherein the output member is a planetary carrier (4); the transmission assembly comprises several groups of planetary gears (3) provided on the planetary carrier, input ends of the planetary gears are engaged with the input teeth, and other ends thereof are engaged with the fixed teeth; and per unit time, the ratio of the number of teeth passed by a planetary gear engaged with the fixed teeth to the number of the fixed teeth is equal to the ratio of the number of teeth passed by a planetary gear engaged with the input teeth to the number of the input teeth. The two-speed transmission, which comprises the bidirectional overrunning clutch, further comprises a shunting assembly and a brake (009), wherein the shunting assembly comprises an input member (008) and two shunting members (005, 007), one of the shunting members is fixedly connected to the output member of the bidirectional overrunning clutch, the other shunting member is fixedly connected to the input teeth of the bidirectional overrunning clutch, and the brake is used for controlling the input of the bidirectional overrunning clutch; and the input of the shunting assembly is a two-speed transmission input, and the output of the bidirectional overrunning clutch is a two-speed transmission output.
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