Eaton has announced its eMobility business has been chosen to supply a 4-speed medium-duty electrified vehicle (EV) transmission to Proterra, a leading innovator in commercial vehicle electrification technology, for the company's ProDrive drivetrain used in Proterra ZX5 electric transit buses. The medium-duty 4-speed transmission, to be used in city buses in North America, addresses the primary issue related to single-speed drives that have contradictory requirements for high efficiency at top speeds and increased torque at launch and low speeds. The transmission is a lightweight, countershaft gearbox with torque capacity up to 1,200 Nm (885 lb.-ft.) and electric gearshift actuation that enables manufacturers to use smaller, more efficient motors.

Eaton's 4-speed transmission has fine-pitch helical gears that ensure smooth, low-noise operation and a shifting strategy designed to extend range and battery life. Road tests have shown a 20%­ to 30% efficiency improvement in energy consumption under normal driving conditions compared with a direct-drive transmission and a 10% to 15% improvement compared with a current 2-speed solution.