General Motors Electro-Motive Division built just seven SD45X diesels in 1970 – four demonstrators and three for Southern Pacific Railroad. EMDX 4201-4203 were built with SP's typical array of signal lights on the cab and nose, and eventually became SP 9503-9505, joining SP SD45Xs 9500-9502 on the roster.
Visually similar to the builder’s SD45 diesels, the SD45X was longer and utilized four radiator fans. (There were a lot of other spotting features as well, but those are the two primary differences.) It was hoped that solve overheading issues caused by operating in the many tunnels on SP's line across Donner Pass, and they were a slight improvement. But SP's experiments with "elephant ears" on SD45s worked well enough that EMD inverted the cooling apparatus on the SD45/SD45-2 to create the SD45T-2 (and later SD40T-2) locomotive for the SP. But, back to the SD45X…
EMDX SD45X 5740, seen here on the Kansas City Southern, was a single unit demonstrator, built in June 1970. Curiously, this unit's roadnumber is the same as its frame number (5740-1). The 5740 was a demonstrator the entire time, and was also the last SD45X to exist, following the retirement and eventual scrapping of the other six. (Kansas City, Missouri – October 24, 1979)
