A body-powered wearable robot (BPWR) transmits power from one joint to another in an exoskeleton. A variable hydraulic transmission design using long-stroke rolling diaphragm cylinders and efficient on/off valves is suggested in this paper to be used in a BPWR. Using the new design, a high number of transmission ratios are achievable in a smooth mechanism. The number of transmission ratios with respect to the number of cylinders and the pressure drop across the transmission is assessed. The torque loss caused by the pressure drop is 5 percent using a proper conduit geometry.