Fleet Maintenance - 12

only two of those tires are powered, they can tend
to wear faster.
A 6x2 pusher axle helps reclaim some of those
downsides. First of all, the powered drive axle
remains in the far back which
aids traction. Secondly,
due to the fact that
it is positioned
upfront, a pusher
axle can be lifted
when not needed, which helps
reduce tire wear.
According to Steve Mastroianni,
senior manager of product planning
for axles at Dana, a leading drivetrain
and propulsion systems provider, a tag
axle is more than adequate in areas south
of Interstate 40, which runs east to west
from northern Arizona through North
Carolina. That is because those southern
environments present minimal scenarios
where traction is significantly compromised
due to weather conditions.
When operating in more northern environments, Mastroianni says a pusher configuration
becomes more favorable. "A pusher definitely has
some advantages in places where there is inclement weather," Mastroianni says.
"With a pusher axle, drivers can sort of 'stretch
the wheelbase' by applying power far back behind
the fifth wheel where they're probably going
to have more of a weight loading," says Scott
Donnelly, aftermarket training and senior quality
engineer for Dana.
Conversely, with a tag axle, power is applied at
the forward axle.
"The rear axle of a tag is still going to provide
stability and load-carrying capability," Donnelly
points out.
The type of 6x2 configuration that makes the
most sense for a fleet will depend on what the
tractor-trailer is transporting, where the load is
being transported, and how often the truck travels
with a less-than-full load.

»Dana's EconoTrek 6x2 tandem axle consists of the S175 front drive axle and a unique rear
tag axle. The tag axle has a square-edge banjo housing design for enhanced durability. The tag
axle is also optimized for electronic-controlled load distribution air suspension systems.
Photo courtesy of Dana

"Some fleets prefer wide-base singles
while others prefer dual tires. Some
like torque-reactive suspensions
while others do not. There are all
kinds of tweaking fleets can do with
6x2s to get the most favorable vehicle
dynamics they are looking for."
Steve Mastroianni, senior manager of product planning for axles, Dana Inc.

Benefits of 6x2 axles

The primary benefit of using a 6x2 axle is
improved fuel economy as only one of the rear
axles is powered. When the non-powered axle is
liftable in the pusher position, the fuel savings
can be even more impactful.
"A liftable pusher axle reduces rolling resistance which further improves fuel economy,"
says Michael Hof, vice president of business
development for Link Manufacturing which
offers a 6x2 liftable pusher. "Some fleets that are
more experienced with 6x2 pushers are getting
anywhere from 10 to 12 miles per gallon." Data
on Link Manufacturing's website suggests a 3 to 5
percent improvement in fuel economy compared
to a 6x4 axle.
Roy Horton, director of product strategy for
Mack Trucks, a manufacturer of heavy duty Class
8 trucks, engines, and transmissions, notes that
depending on the application, 6x2 pusher axles
can provide substantial cost and time savings
to a fleet.

12 Fleet Maintenance | April 2020

"Applications involving light loads or driving
empty on one leg of a route are good examples,"
Horton says.
Mack's Liftable Pusher Axle features weight
sensors in the truck that can detect an empty,
partially full, or full trailer and automatically
raise or lower the pusher axle to help maximize
fuel efficiency.
"The system also automatically distributes
weight between the pusher and rear axle to
enhance traction," Horton says. Drivers can manually override the system as needed.
Hendrickson, a manufacturer of truck, tractor,
bus, and recreational vehicle suspensions, axles,
and other products, manufactures its own liftable
pusher axle.
"Our Optimaax forward liftable axle lifts when
the tractor is lightly loaded or in a bobtail for
additional fuel economy," says Mark Williamson,
on-highway segment manager for Hendrickson.

Reduced weight is a second benefit of 6x2 axles.
As Link Manufacturing's Van Den Brink points
out, since the non-powered axle doesn't need internal gearing or a driveshaft, it can shed several
hundred pounds. This can be an important benefit to fleets that are especially concerned about
weight and cargo-carrying capacity.
Hendrickson's Williamson says a 6x2 pusher is
ideal for a fleet with diminishing load applications
such as bulk haulers, grocery, livestock, beverage,
or applications experiencing empty back hauls.
Fleets can also reduce their tolls with a liftable
pusher axle.
"Lifting an axle reduces axle count," Van Den
Brink says.
As touched on earlier, Williamson says a
common complaint from drivers who have run
6x2s is lack of traction, especially when backing
under a trailer. However, when a tractor is config Continued Page 14

Fleet Maintenance

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