The ten members of the 70 Class delivered by Commonwealth Engineering from 1960 were very different from the diesel locomotives ordered before them. As well as being diesel-hydraulic rather than diesel-electric, these locomotives were of an 0-6-0 design rather than a more conventional Bo-Bo or Co-Co wheel arrangement. Their light axle load was specified to allow them to work on the industrial branch and wharf lines in the Port Kembla (Wollongong, NSW) area. The introduction of the 70 Class would see the demise of Thirroul loco and the collection of steam locomotives used as shunting locomotives at Port Kembla.

As well as being used to shunt the wharves at Port Kembla, 70 Class locomotives also shunted other yards in Sydney including Darling Harbour and Chullora. The class were also occasionally used on Wollongong suburban passenger trains.

The class was withdrawn between 1984 and 1986. 7006 was the final locomotive in the class to be used in service, withdrawn on September 11th, 1986. 7006 outlasted classmate 7010 by one day, with 7010 set aside on September 10th.

7006 is operationally preserved at Thirlmere, whilst Dorrigo Steam Railway & Museum also own three class members.