“Today’s emission-controlled engines are heavier. I will need the weight savings of a 6x2 to offset some of that increased weight.” 

Fleet Owner

Executive Summary

Fleets switching their tractors to 6x2 axle configurations could realize a 2.5% fuel reduction and a 20-month payback, among other benefits, according to data gathered from interviews, pre-existing studies, and test from seven fleets and two truck manufacturers. 

We have also developed a Payback Calculator, and an initial decision-making tool, to help fleets determine whether the best practices for 6x2 performance are relevant or replicable in their own operations. 

Introduction to 6x2
Available Systems

A 6x2 axle configuration has three axles and six wheel-ends, but only one of the rear tandem axles (two wheel-ends) is actually powered by the engine.  The non-driving axle often is referred to as a “dead” axle, and the whole 6x2 system is often called a “dead axle tandem.”1

  • 1. There are two possible configurations of the 6x2 system, differentiated by the location of the non-driving axle.
    • The most common is the tag tandem where the forward-rear axle is driven and the rear-rear axle is the non-driven or tag axle.
    • A “pusher tag” 6x2 system has the non-driven axle in the forward-rear location and the drive axle in the rear-rear location.

    Dana Holding Corp., Detroit, and Meritor, Inc. are currently producing 6x2 systems for the North American market

    Detroit offers a 6x2 axle as part of its integrated power train. The 6x2 configuration has a 2.28 ratio specifically designed to work with downsped engine ratings. It incorporates a nondriven tag axle on the tandem which reduces weight by almost 400 lbs.

    In the spring of 2013, Dana introduced its newest 6x2 system, the Spicer EconoTrek tandem. It reduces overall weight by up to 450 lbs. compared to a traditional 40,000 lbs. tandem axle arrangement. The system combines the company’s Spicer S170 or S190 single reduction single-drive axle with a Spicer S20-045B that serves as the non-driven or tag axle.

    Meritor offers the FUELite 6x2 system, the first tandem axle set in the company’s 6x2 configuration family, the SoloDrive Series. Based on the company’s 160-Series drive axle, the FUELite 6x2 system offers 400 lbs. of weight savings when compared to a similar 6x4 configuration. The system includes Meritor DualTrac housings and a rectangular tag axle.

Common Fleet Strategies

To achieve the best fuel economy with 6x2 axles, fleet purchase them with these other components: 

  • Single wide-base tires on the drive axle
  • Ribbed low-rolling resistance wide-base trailer tires on the tag axle
  • A direct-drive transmission
  • A gear fast, run slow rear-axle ratio approaching 2.50 and filled with low-viscosity synthetic lube
What Others Are Saying
Decision-Making Tools

The study team developed several tools to help fleets in making their decision about 6x2 axles.

Payback

The payback calculator estimates the payback in months for end users who adopt 6x2 technology. Fleets input data into the form and the calculator uses that data along with information gathered by the study team to quantify the benefits and consequences likely to be experienced by the fleet in terms of upfront costs and year-over-year costs.

Manufacturers

Currently three suppliers make 6x2 axles.

Conclusions

Major study conclusions include:

  • Axle manufacturers and truck builders have integrated 6x2s into their products; there is widespread availability.
  • An aggressive adoption of 6x2 axles on new trucks is predicted over the next few years, possibly doubling every year.
  • Fuel economy improvements of 2.5% and paybacks of 20 months are normal.
  • There is a great deal of data and test results around fuel efficiency, traction, tire wear, and resale value. Confidence in 6x2 as a good investment is medium to high. 

For more details on 6x2 axles, download the entire Confidence Report by clicking here.