In 1965 and 1966, the South African Railways placed sixty-five Class 33-000 General Electric type U20C diesel-electric locomotives in service.

[3] The two GE-built Classes were virtually identical in appearance, but could be distinguished from each other by some ventilation openings on their bodywork.

These doors and panels could get swapped between models and sometimes did, either as replacement for damaged items or by chance during overhauls.

Some were later employed as heavy shunting engines to assemble or unload iron ore trains at the Sishen-Saldanha iron ore line's terminals, until the arrival of the Class 43-000 on that line in 2011 made more GE-built Class 34 locomotives available for this task.

A few were leased to Sudan Railways on a long-term contract as a result of the distance from South Africa, while others were sold to COMILOG in Gabon.

[5] In 2013 some Class 33-000 locomotives were sold to Corredor de Desenvolvimento do Norte (CDN) at Nacala in northern Mozambique.

[6] The Class 33-000 builder's works numbers, service in the Zambia Railways leasing pool and known eventual disposition are listed in the table.