The 40 class were the first mainline diesel electric locomotives to be built for the New South Wales Department of Railways.

With major electrical work required and their lack of power compared to other diesels, the 40 class were withdrawn from May 1968 with the last being taken out of service in December 1971.

It was returned to traffic in October 2010 painted in the blue livery it received in 1954 to haul the Royal Train.

[6] Robe River Iron Associates purchased 4002 and 4006 for use on construction trains and later as shunters in the Pilbara region of Western Australia where they were renumbered 9405 and 9401.

A representation of the 40 class has previous been made by modifying an Atlas RSD-4/5 model both in HO and later in O scale, primarily by replacing the cab and making several detail changes, though retaining the incorrect unequal axle spacing of the Co type bogie instead of the correct A1A type.