Around the world, we Americans seem to have a reputation for indulging in excess. And maybe it’s justified. Take drive axles, for example.
While European fleets almost exclusively use an economical, single drive axle, with a tag or pusher to help support the load – a 6 x 2 setup – here we insist on tandem drive axles – or a 6 x 4 arrangement – in high GCW applications. Why is that?
“It’s mainly a matter of better traction,” says Jim Trotter, product manager of ArvinMeritor’s suspension group. “Plus, a 6-by-2 would suffer here at resale time.”
So how do they get by with a single drive in Europe? “For one thing, we don’t have as much of the extreme weather that you guys get,” says Brian Weatherley, editor-in-chief of Commercial Motor in the U.K. “When we do, we use tire chains for traction. We don’t need a tandem, except for trucks that go off-road. And, we’re extremely weight-conscious – a tandem drive eats into payload.”
Also, diesel is much more expensive in Europe. “Powering a second drive axle consumes extra fuel,” adds Weatherley. “Fuel costs so much here that we’ve never even had an idling problem.”
Now the question: Could we realize the advantages of a 6 x 2 setup on this side of the pond if the traction and resale issues were solved? Dana thinks so, and is developing, for introduction next year, a clever system consisting of a high-entry, single drive axle and a reconfigurable tag axle.
To address the traction concern, the air bags of the tag axle are exhausted when the differential lock is engaged, explains Leo Wenstrup, Dana’s senior product manager of drive axle systems. “This temporarily shifts all the weight to the driven axle at low speed, which gives the same traction as a traditional tandem axle,” he says. So, while the added traction wouldn’t be available at speed, it could – perhaps along with a differential lock – get the vehicle out of a slippery situation.
As for resale value, the tag axle uses a banjo-style housing, and Dana plans to offer a kit to convert it to a second drive axle, which will make the vehicle more mainstream and flexible for the next owner. The kit would be installed at resale time by the selling dealer, and while the price hasn’t yet been set, “it would be less than the increase in market value between a 6-by-2 and a 6-by-4,” says Wenstrup.
Meanwhile, the first owner would save about 200 pounds and about 14 pints of lubricant, and would eliminate energy losses produced by inter-axle drivelines and rear axle assemblies.
Could the idea catch on? Initially, perhaps, with some forward-thinking, even adventurous, fleets. But I think, for better or worse, it’ll take some time to convince an entire industry as conservative – and American – as ours.
