Hybrid Electric Powered Axle

A 6×4 chassis can now have both an engine driven axle and an electrically driven axle.  The regenerative braking can not only save on brake wear, the energy can be captured in situations where additional power is beneficial such as vehicle launch or steep/lengthy inclines to decrease fuel consumption. Effectively the vehicle is a 6×2 when normal efficient operation is desired and becomes a 6×4 when it is most beneficial.


Little data is available for these systems, but the potential is there for a double-digit percentage improvement in fuel economy depending on the terrain traveled and duty cycle of operations.

The storage battery can supply power to other electrical systems if so designed to reduce idling (such as powering the sleeper air conditioning system or accessory “hotel” loads).


The system adds 400 to 500 pounds to the tractor.

The system adds several expensive components including an automated control system.

Introduction & Rationale

Formula One race cars utilize regenerative braking as do numerous models of electric and hybrid passenger cars.  An electric drive axle is used for the rear tractor axle in this strategy.  During downhill runs and during braking situations, the axle powers an electric motor-generator which stores the generated electric power in a lithium ion battery pack.  When appropriate for power to be applied via this axle the process is reversed to keep the diesel engine operating most efficiently.

Available Systems

A few suppliers have developed electric axles and these systems are now in validation.  One supplier provides a complete solution which combines their electric axle with the battery, an electric AC system and the controlling software.


  • Hyliion
  • Meritor
  • Dana