By the 1950s, railroads were shopping for more powerful units to replace
earlier diesels, and a horsepower race between EMD, ALCO and General
Electric began in earnest. GE took a bold step forward, unveiling its
brutish new Universal series in 1959. Production began with a
2500-horsepower, four-axle unit, known as the U25B in 1960 -- and railfans
quickly nicknamed them U-boats. The success of the new series soon pushed
GE into the number two spot in locomotive sales.
In 1966 a 2800-horsepower prime mover was added to create the U28B. Only
148 units were built that year. Late production units had a shorter nose
and some differences in the radiator intakes, which were carried over into
early U30B production. Late in 1966, GE introduced a 3000 horsepower prime
mover in the U30B. Many features were carried over into the new body
however later production units (the prototypes for these models) had
revised air intakes. Total production ended at 296 units in 1975.