1,260 were built for American railroads before the SD45-2 replaced it. Other models, like the SD45T-2 'Tunnel Motor', were released in 1972.
SD45s had several teething problems. Reliability was not as high as anticipated; the twenty-cylinder prime mover could break its own crankshaft. Though it produced 600 horsepower (450 kW) more than the 16-645E3 in the SD40, some railroads felt it wasn't worth it, even after EMD redesigned the block to reduce crankshaft flexing, thereby producing the 645F crankcase and crankshaft. But, the redesigned block and crankshaft formed the basis of the exceptionally reliable 710G engine, which is the cornerstone of EMD's current offerings.