EMD GP40

The EMD GP40 entered production in November 1965 as General Motors' Electro-Motive Division responded to railroad demand for a higher-horsepower four-axle road switcher. It succeeded the GP35, which had been powered by the older 567D3A engine, and represented EMD's first application of the new 645 series prime mover in a standard B-B road switcher configuration. The GP40 delivered 3,000 horsepower, a significant step up that made it attractive to major American railroads seeking to consolidate their fleets around fewer, more capable locomotives. Over the course of its production run, which concluded in December 1971, a total of 1,243 GP40s were built. The vast majority served American carriers, with 1,187 units going to 28 different United States railroads. Canadian National took delivery of 16 units, while two Mexican railroads, Ferrocarril Chihuahua al Pacífico and Ferrocarriles Nacionales de México, together accounted for 18 more. Norfolk and Western Railway received a notable batch of 60 units built with high short hoods and dual control stands, reflecting that railroad's operational preferences. On January 1, 1972, EMD replaced the GP40 with the GP40-2, which incorporated a modular electrical system derived from lessons learned during the earlier model's service life. The GP40's legacy extended well beyond its original production. Union Pacific eventually rebuilt 129 of its GP40s and GP40-2s into GP40N variants at its Jenks Shop, equipping them with microprocessor control systems to improve adhesion and extend service life. The St. Louis Southwestern Railway converted eight of its units into GP40R locomotives in 1982. More recently, the GP22ECO program has reused GP40 frames, trucks, and carbody components while replacing the original prime mover with a modern 8-710-ECO engine, demonstrating the enduring structural value of the original platform.

The GP40 is powered by an EMD 645E3 sixteen-cylinder engine producing 3,000 horsepower, driving the locomotive through a direct-current electrical transmission system. The locomotive rides on a B-B wheel arrangement, meaning two two-axle powered trucks, with all four axles motored. EMD constructed the GP40 on a 55-foot frame, which is approximately three feet longer than the 52-foot frame used on the GP35 and several earlier GP-series models. This additional length was necessary to accommodate the larger 645 series engine and its associated cooling requirements. The expanded cooling system is visually distinctive, featuring three 48-inch radiator fans mounted at the rear of the long hood, compared to the two large fans and one smaller intermediate fan found on the GP35. A practical field identification detail is the number of handrail stanchions along the long hood: the GP40 has ten, while the GP35 has nine, directly reflecting the difference in frame length. Two passenger-oriented variants were developed alongside the standard freight version. The GP40P and GP40TC were both built on longer frames than the standard model in order to house steam generators or head-end power equipment needed for passenger train service. These variants shared the core mechanical components of the freight version but were tailored to the specific operating requirements of passenger carriers. The fundamental reliability and power output of the 645E3 engine helped establish the GP40 as a well-regarded locomotive in an era when railroads were actively consolidating onto higher-horsepower diesel power.

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