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.


Buyers included the Burlington Northern, Southern Pacific, Santa Fe, Pennsylvania Railroad, the Great Northern Railway, Union Pacific and the Northern Pacific Railway. (Contrary to enthusiast legend^{[according to whom?]}
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^[when?] retired the entire fleet, with mass scrappings. Montana Rail Link is also starting to sell some for scrap.