6x2 Efficiency and 6x4 Performance: Fleets Can Have it All

Dana's Dual Range DisconnectTechnology Promotes Drivetrain Efficiency for Commercial Vehicles

  Dana's new Spicer  ®     AdvanTEK  ®     Dual Range Disconnect  ™     concept has been designed for tandem axles used in Class 8 linehaul applications. 

Dana's new Spicer® AdvanTEK® Dual Range Disconnect concept has been designed for tandem axles used in Class 8 linehaul applications. 

The commercial vehicle industry is looking for new ways to increase efficiency and improve fuel economy to meet toughening U.S. standards and reduce fuel costs. Technologies to simplify the driver experience are also growing in importance as a way to support operators, especially those with less experience who are not as familiar with techniques to optimize the performance of their trucks. While still important, basic fuel savings practices such as reducing idle time and keeping up with routine maintenance do not address the kind of fuel economy gains that OEMs require to meet these new standards. To achieve this level of efficiency requires high-level, innovative technology that doesn’t complicate vehicle operation.

The need for increased efficiency is urgent for commercial-vehicle fleets. A recent proposal from the United States Environmental Protection Agency and the National Highway Traffic Safety Administration introduced Phase 2 standards to further improve fuel efficiency and reduce greenhouse gas emissions for medium- and heavy-duty vehicles. The proposed standards are achievable through technologies such as higher-efficiency engines running at lower rpms and quick, precise-shifting transmissions, along with the drivetrain components that optimize their performance.

Slow Acceptance of the 6x2, Despite Efficiency Gains
Popular in Europe, the highly efficient 6x2 drive axle has been on the U.S. market for decades, offering a verified fuel efficiency increase of approximately 2.5 percent when compared with a traditional 6x4 configuration. A single drive axle with power going to two wheels, the 6x2 is both lightweight and heavy duty. But a variety of concerns have prevented many fleets from making the switch, despite the proven fuel savings and weight reduction. A recent study from the North American Council for Freight Efficiency reported on the efficiency benefits of 6x2 axles, but also documented the barriers to acceptance of this technology in the United States.

One obstacle to overcome is building confidence in the OEM as a knowledgeable resource for information on new technology. Fleets trust the experience of other fleets more than any other source. With limited data on 6x2 early adopters, fleets worry about getting ample traction with power to only two wheels, leading to a hesitation to spec new linehaul tractors with this configuration. Tire wear, resale value, and driver acceptance are additional concerns.

Industry-Leading Technology Combines Efficiency and Performance
Enter the new Spicer® AdvanTEK® Dual Range Disconnect concept, bringing together the best of both worlds. This industry-leading technology improves efficiency without sacrificing performance by seamlessly combining the traction and dependability offered by a 6x4 configuration with the reduced drivetrain losses and improved fuel economy of a 6x2 configuration.

At startup, on grades, at low speeds, during backup maneuvering, or in other environments where additional traction is needed, the technology allows the tandem axle to operate as a 6x4. As the truck nears a predetermined speed or event, an electronic control unit (ECU) in the axle coordinates with engine and transmission ECUs to disconnect the inter-axle shaft from the power divider in the forward drive axle. It also disconnects power from the axle shaft in the rear drive axle, allowing for operation in a more efficient 6x2 mode. At the same time, it shifts the forward axle to a faster ratio that enables the engine speed to decrease to as low as 900 rpm for highway cruise operation. Without any additional action required from the driver, the axle can be configured to shift between 6x2 and 6x4 at a point preset by the manufacturer. This point can be a certain gear, speed, or other variable.

Optimized for trucks that implement engine downspeeding, this breakthrough tandem axle technology improves efficiency without sacrificing performance by seamlessly combining the traction and dependability offered by a 6x4 configuration with the reduced drivetrain losses and improved fuel economy of a 6x2 configuration. The system can enable an estimated overall powertrain system efficiency from 2 to 5 percent when compared with conventional 40k tandem axles paired with overdrive transmissions commonly used today.

By using separate axle ratios for low- and high-speed operation, linehaul trucks are also able to accelerate from low velocity to highway cruise speed much more quickly than a 6x4 or 6x2 tandem axle with a single, fast ratio. Spicer AdvanTEK Dual Range Disconnect technology improves fuel efficiency by reducing drivetrain losses in the inter-axle power divider, inter-axle shaft, and rear drive axle gearing; enhances net engine efficiency by better complementing engine torque curves; and avoids increasing overall powertrain system weights. 

In addition to these efficiency benefits, the Spicer AdvanTEK Dual Range Disconnect concept reduces weight with the use of fewer gears in the transmission. Launchability, gradeability, driveability, and low-speed maneuverability are all improved by operating at a higher numeric axle ratio without the need for larger engine mounts and frame rails.

Dana unveiled this concept at the 2015 Mid-America Trucking Show in Louisville, Ky., where Spicer AdvanTEK Dual Range Disconnect technology could be experienced in action through rides in Dana’s test truck. After conducting evaluations for nearly three years, Dana is moving forward with plans to integrate axles featuring this technology into manufacturers’ chassis for field testing.

We’d like to hear your thoughts. 

  • What concerns do you have with a 6x2 axle configuration?
  • What is appealing about the ability to switch between 6x2 and 6x4 mode?
  • What will it take to achieve these new government efficiency standards for medium- and heavy-duty vehicles?
  • How important is it to maintain performance at low-speed operation with engine downspeeding trends (faster axle ratios)?
  • What do you need to be comfortable adopting new truck technologies?

    Published by Ryan Laskey



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