A powertrain (100) for an electric bicycle has: an electric motor (104); a motor gear (226) connected to the motor (104); a crankshaft (108) for connecting to crank arms (110); an input shaft (232) driven by the crankshaft (108); an input gear (234) connected to the input shaft (232) and driven by the motor gear (226); a plurality of first gears (236) mounted to the input shaft (232); a countershaft (242); a plurality of second gears (244) rotationally mounted to the countershaft (242), each second gear being driven by a corresponding first gear (236); a plurality of third gears (246) rotationally mounted to the countershaft (242); an output shaft (114); a plurality of fourth gears (260) mounted to the output shaft (114), each fourth gear (260) being selectively driven by a corresponding third gear (246); a first shift assembly (248) for selectively rotationally fixing any one second to the countershaft (242); a second shift assembly (250) for selectively rotationally fixing any one third gear (246) to the countershaft (242); and a drive sprocket (116) driven by the output shaft (114).