The SD45 is a six-axle road switcherdiesel-electric locomotive built by General Motors Electro-Motive Division between 1965–1971. It has an EMD 645E3 twenty-cylinder engine generating 3,600 hp (2,680 kW) on the same frame as the SD38, SD39, SD40, and SDP40. As of 2021, most SD45s have been retired, scrapped or rebuilt to SD40-2 standards.
1,260 were built for American railroads before the SD45-2 replaced it in 1972, along with the related SD45T-2 'Tunnel Motor'.
SD45s had several teething problems. Reliability was not as high as anticipated; the twenty-cylinder prime mover was prone to crankshaft failure from engine block flex. Though it produced 600 horsepower (450 kW) more than the 16-645E3 in the SD40, some railroads felt the extra horsepower wasn't worth it, even after EMD strengthened the block to eliminate crankshaft failures. At low speeds, when tractive effort was adhesion-limited, the SD45 provided no advantage over the SD40.
Buyers included the Burlington Northern, Southern Pacific, Santa Fe, Pennsylvania Railroad, the Great Northern Railway, Union Pacific and the Northern Pacific Railway. Many SD45s still exist, some rebuilt with sixteen-cylinder 645s for lease companies. SD45s and SD45-2s owned by Montana Rail Link retain their 20-cylinder prime movers. Wisconsin Central used to roster a large fleet of SD45s, but its sale to CN has resulted in the retirement of the entire fleet, with mass scrappings. Montana Rail Link is also starting to sell some for scrap.
Great Northern 400, named "Hustle Muscle", was the first production SD45. It is preserved by the , based out of Saint Paul, Minnesota. It was in active service on the Minnesota Transportation Museum's Osceola and St. Croix Valley Railway until it suffered a crankshaft failure in its original 20-645E engine, requiring a replacement engine to be installed. BNSF Railway overhauled a 20-645E engine from a retired ex-ATSF SD45-2 and donated and installed the new engine in January 2019.[citation needed]
NP 3617, a preserved SD45 in Minnesota
