In 2000 Transwerk, later Transnet Engineering, started to rebuild class 6E1 locomotives into class 18E in their Koedoespoort shops in Pretoria. Some had previously already been rebuilt to classes 16E and 17E. The most visible difference were the missing windows on one end since one cab had been stripped of all controls. They also got a more modern air brake system and the regenerative brake had been rebuilt into a rheostatic one. Latter had become necessary since the resistor grid banks at substations were unreliable, sometimes leading to the problem that electric energy produced by a braking locomotive could neither be absorbed by another locomotive nor dissipated at the substation. Additionally, the electronics of the locomotives were updated with the help of micro-processors. By 2009, 446 had been rebuilt which were designated “series 1”. 279 more had been rebuilt in 2015 when the rebuilding program was halted in favor of the production of new locomotives. These were designated “series 2”.