To replace steam locomotives on the South Island, the NZR ordered a total of 64 D^J diesel locomotives in the late sixties from Mitsubishi Heavy Industries. Due to a lower price, they won the tender against designs from EMD, English Electric and AEI. To reduce axle load and increase flexibility in curves, they had a Bo-Bo-Bo wheel arrangement. After the electric class E^W, they were the first diesel locomotives in New Zealand with this configuration. But in contrast to the E^W, the body was not split into two halves.

The original engine could produce 1,050 hp for five minutes and 975 hp for an hour. The AC generator was coupled to a rectifier and created direct current for the traction motors, making them the first locomotives with AC/DC transmission in the country. As the engine had reliability issues, it was quickly de-rated to 797 hp. In the late seventies all locomotives were rebuilt with new Caterpillar D398 engines, delivering 840 hp and being more reliable.

The D^J was built without any heating system for passenger trains, but was also used in passenger service with separate steam heat vans. In freight service they were often used double-headed, also together with the class D^G. Another popular use of the D^J was banking on the inclines on the west coast. The first locomotives were withdrawn in 1986 and by 1991, none remained in regular service. Today seven are being owned by Dunedin Railways. Only four of these are operational on their Taieri Gorge Railway.