The purpose of this paper is to describe comparative fuel economy testing of two-speed and single speed truck axles and to present data showing the fuel-saving capability of a two-speed versus a single speed axle. Fuel economy test results of a medium duty truck equipped first with a manual transmission and then with an automatic transmission, and both in combination with single speed and two-speed axles, is provided at varying gross vehicle weights. The two-speed axle with ratios straddling the ratio of the single speed provided substantial fuel savings when used as a transmission range extender at highway speeds.
