The class formed[when?] the backbone of the NMBS/SNCB shunter fleet. Class 77s have replaced them [when?] but they are still to be found across Belgium [when?]. They were built in three batches: 7301-7335 during 1965–1967, 7336-7375 during 1973-1974 and finally 7373–7395 in 1976–1977.