The EMD F7 is a model of diesel-electric locomotive produced between February 1949 and December 1953 by the Electro-Motive Division of General Motors (EMD) and General Motors Diesel (GMD). Although originally promoted by EMD as a freight-hauling unit, the F7 was also used in passenger service hauling such trains as the Santa Fe Railway's Super Chief, & El Capitan and Ontario Northland's Northlander. History The F7 was the fourth model in GM-EMD's successful line of F-unit locomotives, and by far the best-selling cab unit of all time. In fact, more F7s were built than all other F-units combined. The F7 succeeded the F3 model in GM-EMD's F-unit series, and was replaced in turn by the F9. Final assembly was at GM-EMD's La Grange, Illinois, plant or GMD's London, Ontario, facility. There was no F4, -5 or -6 model; "7" was chosen to match the contemporary twin-engine E7, and was also applied to the new GP7 road-switcher. The F7 differed from the F3 primarily in internal equipment—mostly electrical—and some external features. Its continuous tractive effort rating was 20 percent higher, e.g. for an F7 with gearing, compared to for an F3 with the same gearing. A total of 2,393 cab-equipped lead A units and 1,463 cabless-booster or B units were built. Many F7s remained in service for decades, as railroads found them economical to operate and maintain. However, the locomotive was not very popular with yard crews who operated them in switching service because they were difficult to mount and dismount, and it was also nearly impossible for the engineer to see hand signals from a ground crew without leaning way outside the window. As most of these engines were bought and operated before two-way radio became standard on most American railroads, this was a major point of contention. In later years, with the advent of the "road switchers" such as the EMD GP7, F-units were primarily used in "through freight" and "unit train" service where there was little or no switching to be done. Engine and powertrain The F7's prime mover is a 16-cylinder 567B series diesel engine developing at 800 rpm. The 567B is a mechanically aspirated two-stroke design in a 45-degree V engine configuration, with displacement per cylinder, for a total of . A direct current generator that is mechanically coupled to the flywheel end of the engine powers four traction motors, with two motors mounted on each