The SD45 is a six-axle diesel-electric locomotive built by General Motors Electro-Motive Division between December, 1965, and December, 1971. It had an EMD 645E3 twenty-cylinder engine generating 3,600 HP. It had the same frame as the EMD SD38, EMD SD39, EMD SD40, and EMD SDP40.
1,260 units were built for American railroads before the SD45-2 appeared as its replacement. Other models, like the SD45T-2 'Tunnel Motor', were released in 1972.
SD45s had several teething problems. Reliability was not as high as anticipated, due to the twenty-cylinder prime mover's propensity to break its own crankshaft. Though it produced 600 horsepower (450 kW) more than the 16-645 in the SD40, some railroads felt it wasn't worth it, even after EMD redesigned the block to reduce crankshaft flexing.
Buyers included the Southern Pacific, Santa Fe, the Great Northern Railway, Union Pacific and the Northern Pacific Railway. (Contrary to what many believe, the SD45 was not a "gas guzzler." It produced more power per unit of fuel than its 3,000 hp (2,240 kW) counterpart, the SD40. It did consume more fuel at idle than the 16 cylinder prime mover in the SD40, and at the time US railroads typically left a locomotive idling when not in use.) 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 recently retired the entire fleet, with mass scrappings. Montana Rail Link is also starting to sell some for scrap.
- Great Northern Railway 400. The first production SD45 named Hustle Muscle. Owned by the Great Northern Railway Historical Society, the unit is operable.
- Pinkepank, Jerry. Diesel Spotters Guide 2.
- Diesel Spotter's Guide, Volume 2. Kalmbach, 1994.
- White, Dr. W. J. How Diesel Electric Locomotives Operate. Peat. 1998.