In 1992, GM's Electro-Motive Division (EMD) introduced its new SD70 series of third-generation, computerized diesels. The standard DC-motored version was the SD70M, while the SD70MAC offered AC traction motors - a technology that would later become the new standard for mainline diesels. One glance at the design of the new SD70 series revealed enormous technological gains in railroading.
The engines boasted a 32-bit 16MHz control microprocessor named the EM2000. This computer worked with an Integrated Cab Electronics (ICE) system to collect, analyze, and display a range of accurate-to-the-second information, including speed, amps, throttle position, air brake operation, and cab signals. All of this information was displayed on full-color LCD displays that replaced the gauges and indicators on earlier diesels.
The 70 Series also employed an HTCR (high-traction three-axle radial) truck that reduced lateral loads and rolling resistance in curves - increasing wheel life by up to 20 percent. By far the largest owner of SD70Ms was, and still is, the Union Pacific, which set a record for the largest single diesel order by purchasing 1000 engines - and later increasing the order by another 500 units. Production of the SD70M ended in 2004, as new EPA Tier 2 environmental regulations led to an upgraded design, the new SD70ACe.
Did You Know?
In 2019, UP SD70M No. 4014 was renumbered 4479, to make room for restored Big Boy 4014 on the Union Pacific's roster.