Eaton transmission for electric vehicles

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Eaton’s eMobility business has a new four-speed transmission for electrified Class 7 and 8 commercial vehicles, and it’s scheduled to debut in 2022.

The model adds to an existing portfolio that includes medium-duty two- and four-speed models that are currently in production.

Tests are currently underway with major OEMs, the company says.

The four-speed transmission solves a key issue linked to single-speed drives – the need for high efficiency at top speeds, and also increased torque when launching the vehicle and at low speed.

Fine-pitch helical gears are responsible for ensuring a smooth, quiet operation, while the Eaton Transmission Control Unit’s shifts support fast gear changes and efficiency to extend range and battery life, the company says.

While the transmission is based on the lay shaft architecture found in automated manual transmissions, it has been designed for electric commercial vehicles. The four-speed EV gearbox doesn’t have a clutch, and the shifts are synchronized using a traction motor. It also operates at higher speeds than gearboxes for internal combustion engines, and the gears are optimized for the power curves of electric motors.

The transmission offers a higher output speed and torque range than a direct-drive system, allowing for smaller electric motors to be used in large commercial vehicles.

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John G. Smith is the editorial director of Newcom Media's trucking and supply chain publications -- including Today's Trucking,, TruckTech, Transport Routier, and Road Today. The award-winning journalist has covered the trucking industry since 1995.

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