In the early years of new energy heavy-duty truck development, central direct drive was almost the standard configuration across the industry. But today, the dual-motor integrated electric drive axle for truck-widely known as e axle for trucks-is quickly phasing out central direct drive. This is not a gimmick or over-engineering by manufacturers; it is a brutal dimensional advantage spanning physical fundamentals and space utilization. Today, we tear down the heavy-duty truck chassis to explain how the traditional transmission chain is being eliminated.
Bulky Central Direct Drive: The Physical Inertia of a Century-Old Fuel Chassis
Central direct drive is essentially a leftover from the "fuel-to-electric" era. Its logic is simple and crude: remove the diesel engine, install a large electric motor, keep the traditional gearbox, and use a long drive shaft to send power to the rear axle differential.
The advantage of this design is extremely low R&D cost, with almost no new molds needed for the chassis. But its physical weakness is fatal: excessive mechanical loss. Power from the motor passes through gearbox gears, a 2–3 meter drive shaft, and the rear axle main reducer, resulting in massive waste of transmission efficiency. What's more, the single motor cuts off power completely when shifting with an AMT gearbox. The terrifying shudder and rollback risk when climbing slopes with a full 49-ton load are every truck driver's nightmare.
Space & Weight Advantages of Electric Truck Axle: Room for Giant Battery Packs
The emergence of dual-motor integrated electric truck drive axle has completely overturned the traditional chassis design. It integrates the motor and gearbox directly into the wheel end or axle housing, eliminating the chassis-spanning drive shaft entirely.
For heavy-duty line-haul logistics, the math is crystal clear:
Unlocked chassis space: Without the drive shaft, a large golden space opens up between the frame rails. This makes under-chassis battery swapping and large 500–600kWh battery pack installation possible. The vehicle's center of gravity is drastically lowered, delivering stable high-speed cornering.
Extreme lightweighting: Removing the traditional gearbox housing, drive shaft and complex mechanical parts cuts hundreds of kilograms from the curb weight. In the tonnage-based freight industry, every kilogram saved translates directly to legal payload and real profit.
This compact layout is the core strength of the e axle system-it redefines how electric axles for trucks fit into heavy-duty vehicle design.
The Ultimate Strength of Dual-Motor Electric Axle: Shift Without Power Interruption
This is the core technical barrier that makes dual-motor electric rear axle dominate the market. Unlike passenger vehicles, heavy-duty trucks carry massive loads; pure motor direct drive cannot climb steep mining slopes, so a gearbox is mandatory to amplify torque.
The brilliance of dual-motor axle with electric motor lies in "teamwork". When the vehicle shifts, Motor A cuts power to complete the gear change, while Motor B keeps outputting torque to drive the truck forward. Once Motor A finishes shifting and takes over power, Motor B completes its own shift.
This "relay race" shifting logic completely eliminates the power vacuum during gear changes. Whether starting with a full load or climbing long slopes, power delivery is silky smooth. It not only erases shift shudder but also pushes overall energy consumption to an extremely low level.
The electric axle drive system achieve seamless power output, making electric motor rear axle the optimal choice for heavy-duty applications.
Conclusion
The replacement of central direct drive by dual-motor integrated electric drive axle is no coincidence-it is an inevitable result of overwhelming advantages in transmission efficiency, chassis space and power smoothness. As electric axle technology matures and costs drop, the buzzing drive shaft is destined to exit the physical stage of new energy heavy-duty trucks for good.
For OEMs and fleet operators, choosing the right truck drive axle means embracing higher efficiency, lower TCO and stronger competitiveness in the electric truck era.