[4] The DFs were powered by an EMD 12-645 engine, the same prime mover chosen for the DC class, but were able to make greater use of that power by having six traction motors and Co-Co arrangement as opposed to the four traction motors and A1A-A1A wheel arrangement of the DCs.

The first 20 members of the DF class arrived in New Zealand in July 1979, and initially, ten worked on the East Coast Main Trunk, Kinleith, Rotorua and Murupara Branches, making use of the recently opened Kaimai Tunnel;[2] and ten worked freight trains on the Main North Line between Christchurch and Picton.

In 1986, the DF fleet was reallocated, concentrating 22 of the class in the South Island, and reallocating the remaining eight North Island DFs from Hamilton to Wellington, for use between Wellington and Gisborne, on the Wairarapa Line and Palmerston North - Gisborne Line (PNGL).

[1] DFT7008 was released from Hutt Workshops on 20 November 1992 and used on a number of revenue and test trains before being relocated to the South Island on 1 December 1992.

Other DFTs have been assigned periodically to cover for when these units undergo maintenance, with DFT7051 and DFB7186 most recently filling this role during the 2011 Rugby World Cup when extra six-car trains were in use.

The units used on passenger services were required to be fitted with fire suppression equipment by the Pike River Mine disaster enquiry.

Prior to the rebuilding to DFT standard, the locomotives received an upgrade in the late 1980s with the introduction of single-manning to improve visibility for the driver; this involved a large single front window replacing the original configuration that had two small windows instead.

Drivers started to notice left-eye fatigue and back issues after long shifts or extended periods driving the locomotives.

The pillar was moved 100mm to the left with the top and bottom sills raised and lowered at the same time to give drivers a better view of the track immediately in front and below.

[13] In the early 2000s, a number of DFTs were fitted with the Maxitrax wheelslip control and received an internal sub-classification of DFM.

This was used in the Amicus computer system only, and the classification was initially not applied to the locomotives themselves which remained identified as DFT.

Although Maxitrax has since been removed from these locomotives, some of the units that were classed as DFM have had the designation applied to them when repainted into the KiwiRail livery.

[19][20] As of August 2022, of all but two of the withdrawn units were returned to service after undergoing rebuilding to DFBs - 7104 was reinstated as a DFT after receiving repairs,[21] while the other, 7117, was scrapped in May 2021 at Hutt Workshops.

A number of DF class locomotives have been involved in derailments and level-crossing accidents that have required repair.

[31] In early 2001, work started to repair the locomotive, which included straightening its under-frame and constructing a replacement cab.