Many have been built (with over 4,000 built, and another 1,000 custom rebuild or build; including the original SD40 units being upgraded or rebuild to "Dash 2" standards), were purchased by many railroads, and are still currently in use.
The EMD SD40-2 is an upgrade to the original SD40 only with modular electronics and other features.
There have been customized versions of the SD40-2: the SD40-2F, a cowl-type unit built only for the Canadian Pacific; the SD40-2W, built with a wide cab; and many other variants as opposed to the original (as listed below).
Many have been built and many still exist as of today, but are slowly in the process of being retired from service on US Class 1 railroads such as BNSF and Union Pacific. CN has been retiring and scrapping many of its SD40-2's and has been buying used Dash 8's to fill the vacancies.
The EMD SD40-2 uses a 16-cylinder 645E3 (645 series) engine from EMD which is turbocharged. It has the fuel capacity of either 3,200 or 4,000 US gallons, has a width of 10 ft 3 1⁄8 in (3.127 m), has a height of 15 ft 7 1⁄8 in (4.753 m) over the rails, and weighs 368,000 lb (170 tons) to 409,000 lb (204.5 tons) depending on the model.
There are many different versions and/or variants of the SD40-2. (Aside from the original SD40.)
- SD40-2F (CP Rail full-cowl carbody version; known as "Red Barns" by enthusiasts)
- SDP40F (Amtrak)
- SD40-2B (Rebuilt cabless version)
- SD40T-2 (Built for the SP and the Rio Grande; has special type of cooling system for transversing tunnels and sheds)
- SD40M-2 (Morrison-Knudsen rebuilds of pre-Dash 2 SD40's or SD45's.)
- SD40-2R (SD40-2 Life Extension Program by UP Jenks Shop)
- SD40N (SD40-2 Rebuild Program by UP Jenks Shop)
- SD40-2W (CN; wide-cab Canadian built variant)
- SD40-2-LNG (Experimental LNG powered SD40-2 used on the BN/BNSF from 1991-1996.) One unit sold to Brazil, while on other unit is now NS #3528.
- SD40-2W-LNG (CN LNG test locomotives, the program has ended and the two units are stored.)
- KCS (Kansas City Southern) #637 was the very first SD40-2 ever built, but was unfortunately scrapped (unlike IC #6071, the first SD40).
- The SD40-2 is considered to be one of the most popular locomotives of many railfans, and is easily distinguishable from other types of power due to the frame "porches" both front and rear.
- Burlington Northern, Union Pacific, Canadian Pacific, and Conrail had the largest fleets of SD40-2's out of all North American Class 1 railroads.
- Several SD40-2s have been built with "snoot" style noses, which are extended hoods on the front of a diesel locomotive meant for housing special radio control components for Locotrol.
- The D&RGW was one of the only US Class 1 railroads to not purchase the SD40-2 during its production..
- NS rebuilt several of their SD40-2 units into SD38-2 designated units for yard and local train service, but are in the process of being converted back into SD40-2 units as of early 2013.
- Two CN (Canadian National) SD40-2W units were converted to use natural gas, and are part of an experiment or program to conserve fuel consumption and make fuel spending more economical for the railroad. (Program has ended)
- BN had two units modified for use as "Dual" fuel units, meaning they could run off diesel fuel carried on board in the fuel tank, or off Refrigerated Liquified Methane from a tender. Units were modified with flared radiators like SD45s and painted in a special paint scheme.
- BN 6330 was an SD40C, repowered by a CAT prime mover. Unit was equipped with SD45 style flared radiators to handle the increased cooling capacity needed for the big CAT prime mover.