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Can a 6×2 drivetrain find its way into the hearts of U.S. truckers?

By on March 21, 2014

Fuel economy still dominates any conversation on trucking. With today’s prices, each percentage point of fuel saved can add up to serious money. Getting 2-3 percent savings without additional cost would interest anyone in the industry. Weight savings can do that, which brings us to 6×2 drivetrains. The North American Council for Freight Efficiency (NACFE) recently ran tests on fuel economy and performance for 6×2 and 6×4 tractor configurations, and the results could change some thinking.

In Europe, trucks have been using only one drive axle for decades. Their combinations often gross more than our 80,000 pounds on five axles. In fact, their 40 (metric) ton class allows GCWR of 88,000 pounds. A typical configuration would have a 4×2 tractor pulling a 3-axle trailer. When they do run 3-axle tractors, they usually have only one drive axle. The other two are the steer axle and a “tag axle” to support the weight.

In North America, we have long preferred 6×4 tractor layouts, with a steer axle and two drive axles. The reason is simple: traction. When trucks had only spring suspensions, there was no way to transfer weight to improve an axle’s traction. With air suspensions, drivers learned to dump air selectively and use a differential lock, but these manual actions were not precise and often had to be done in stressful situations when mistakes can and do happen.

Finding a solution

In 2005, Dana introduced a 6×2 with a “banjo housing” on the tag axle. It would accommodate the differential, drive shaft, U-joints and axles, available in kit form, to convert to a 6×4. The tag axle air bags would automatically dump air when the differential lock was engaged. That limited the traction increase to slow speed use.

A big advance came in 2012, when Meritor introduced its FUELite Tandem Axle mated to the Meritor WABCO Electronically Controlled Air Suspension (ECAS). The ECAS adjusts the tandem’s air bags to optimize traction automatically, eliminating the need for driver intervention.

By eliminating the second axle’s drive gear, nearly 400 pounds are saved. Operators can use the weight savings for added revenue or to further improve fuel economy. By eliminating internal friction losses, fuel savings are increased by approximately 2 percent compared to a typical 6×4 configuration.

Meritor and Meritor WABCO received the Technical Achievement of the Year award for 2012 from the Truck Writers of North America. One week later, at the 2013 Mid-America Trucking Show, Dana introduced their Spicer EconoTrek 6×2 tandem. The EconoTrek is optimized for electronically controlled air suspensions including the Bendix eTrack system, also introduced at MATS.

The Bendix system transfers weight when the drive axle needs more traction. Spicer S170 or S190 axles both incorporate Spicer’s patented wheel-differential locking feature. Weight reduction is also about 400 pounds compared to a 6×4 layout and fuel economy is increased up to 3 percent.

That’s significant, but many truckers are concerned about resale value with 6×2 trucks. Until the concept becomes widely accepted, 6×4 layouts will continue to command higher trade-in values, exceeding the money saved by eliminating the drivetrain mechanism from one axle.

Savings of 2-3 percent can mean $1,000 to $1,500 or more per year added to your bottom line. And by the time you’re ready to sell your truck, my guess is that there will be no trade-in penalty.

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One Comment

  1. Jim Johnson

    April 4, 2014 at 9:53 am

    First, those 6x2s in European countrys don’t leave the Autobahns (or equivalent highways in other countrys). The US just isn’t set up for that.

    Second, the company I drive for bought several tractors with 1 driven axle and a “tag” axle to make a normal 3 axle configuration. I’ve had to pull or push then at least 10 times on dry ground because of potholes or curbing in front of docks and parking lots and at least 20 times because of ice and snow. They are fine for on highway use but are otherwise horrible.

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