The Rover-designed two-speed transfer box shares a common case with the four-speed manual gearbox and has a vacuum-operated centre differential.

March and Simon (1958) also provide the critical comment that, with rare exceptions, bargaining theory has operated in an empirical vacuum.

Vacuum operated actuators open valves to select a longer, 680mm, inlet tract at low revs, increasing the rate of both the airflow and the engine torque.