In order to be able to replace worn-out steam locomotives on non-electrified routes, the NSB ordered three diesel locomotives from NoHAB, MaK and KHD in 1954. The NoHAB locomotive was built under license from the American EMD F series with two driver's cabs and adapted to the European loading gauge. It largely corresponded to the Danish MY (II) series, but was only designed for 105 km/h instead of 133 km/h. In the meantime, the NSB started the “Vekk med dampen” (“Away with the steam”) program, with which the fleet was to be generally converted to diesel and electric locomotives.
Since the Type 64 from NoHAB was superior to the two competitors, NSB ordered further examples of the series now known as Di 3 for the routes that were not to be electrified. They already had the improved engine of the later series MY (II) with 1,950 hp. In contrast to the MY (II), they received traction motors on all six axles and grilles in front of the windscreens to protect against falling icicles from bridges and tunnels as an adaptation to Norwegian conditions. After 32 Di 3a followed three Di 3b, which were actually intended for the Finnish State Railways and had a gear ratio for 143 km/h in addition to the wheel arrangement A1A-A1A.
Among others, the locomotives replaced the Type 49 “Dovregubben” on the Dovrebane in heavy express service. However, some bridges first had to be rebuilt for the higher axle load of the Di 3, so that steam locomotives were used on main routes until 1970. With increasing electrification of the routes in the southern parts of the country, they were pushed into the northern parts of the country, some of which are not electrified to this day.
At the beginning of the 1980s, the steam boiler was replaced with an auxiliary diesel generator to heat newer passenger cars. They were soon replaced by the Di 4, initially in front of passenger trains. From the 1990s they were replaced in freight traffic by the Di 8 and Class 66, while the last passenger trains were taken over by diesel multiple units. After their retirement, some Di 3 were sold to private railways, some of them also coming to Sweden, Italy and Kosovo.
