EMD GP40X

The EMD GP40X was a prototype four-axle diesel-electric locomotive built by General Motors' Electro-Motive Division (EMD) in 1977. It served as a testbed for several features that would later be incorporated into the GP50 and, more prominently, the GP60 models. The GP40X was essentially an upgraded GP40-2, featuring a turbocharged 645F3B 16-cylinder engine rated at 3,500 horsepower. A key element being tested was the improved engine control system intended to enhance fuel efficiency and reduce emissions. Only four GP40X units were ever built, designated as demonstrator units. These locomotives were not sold commercially in their original GP40X configuration. Following the testing period, they were later rebuilt and sold to various railroads.