The EMD SD40-2 is a 3,000-horsepower (2,200 kW) C-C diesel-electric locomotive built by EMD from 1972 to 1989.
The SD40-2 was introduced in January 1972 as part of EMD's Dash 2 series, competing against the GE U30C and the ALCO Century 630. Although higher-horsepower locomotives were available, including EMD's own SD45-2, the reliability and versatility of the 3,000-horsepower SD40-2 made it the best-selling model in EMD's history and the standard of the industry for several decades after its introduction. The SD40-2 was an improvement over the SD40, with modular electronic control systems similar to those of the experimental DDA40X.
Peak production of the SD40-2 was in the mid-1970s. Sales of the SD40-2 began to diminish after 1981 due to the oil crisis, increased competition from GE's Dash-7 series and the introduction of the EMD SD50, which was available concurrently to late SD40-2 production. The last SD40-2 delivered to a United States railroad was built in July 1984, with production continuing for railroads in Canada until 1988, Mexico until February 1986, and Brazil until October 1989.
SD40-2s are still quite usable nearly fifty years after the first SD40 was made, and many SD40s and locomotives from the pre-Dash-2 series (GP/SD 40s, 39s and 38s, and even some SD45s) have been updated to Dash-2 specifications, possibly including downgrading from 20-645E to 16-645E engines, including, certainly, Dash-2 electrical controls, although the pre-Dash-2 frames cannot accommodate the somewhat similar HTC truck in the space allocated to the Flexicoil C truck (the frame is not long enough). Most SD40-2s which remain in service have by now been rebuilt "in-kind" for another 30 to 40 years of service, although a few (under 30) have been rebuilt to incorporate a 12-cylinder EFI-equipped 710G engine.
Faced with a shortage of reliable medium horsepower units for secondary work, Union Pacific outshopped the first of a new series of rebuilt locomotives in 2011. Using SD40-2's as a starting point, the locomotives receive reconditioned components-including generators, traction motors, cabs, and prime movers. They are also equipped with PTC capability and comply with Tier 0+ emissions standards for locomotives built before 1993. Finally, and perhaps most significantly, they are equipped with the NEXSYS control system, allowing for simplified troubleshooting, enhanced wheel slip control, and automatic startup/shutdown capability. Referred to as "SD40N" by UP, the veteran units have a new lease on life and are commonly found on local and transfer runs, or as trim power in yards - often in sets of three.