The class was a new design for Australian conditions based on other locomotives produced by Downer EDI Rail, such as the narrow gauge GT42CU AC purchased by Queensland Rail and Pacific National and the GT46C purchased by Westrail, Freight Australia and FreightLink. The GT42CU AC used a 12-cylinder EMD 710 engine, based on the USA built SD70MAC with scaled down traction motors, while the GT46C used a 16-cylinder EMD 710 engine with DC traction systems. The American SD70ACe was EMD's 2nd generation AC loco with IGBT inverters, but was too large and heavy for the Australian interstate standard gauge network, weighing in at 188 tonnes when the limit was 134 tonnes. In addition, the GT46C design was already at the 134 tonne limit, even before adding inverters, heavier traction motors and more cooling capacity for higher power engine, and there was a requirement that fuel capacity could not be sacrificed. The locomotive has AC traction equipment, with a Mitsubishi Electric package also used on the SD70ACe, including a TA17 traction alternator, CA9E companion alternator and six ITB 2630 traction motors, along with solid state IGBT inverters. The prime mover is a turbocharged 16-cylinder EMD 710. New technology used included passive steer bogies, to reduce flange wear on curves. The class were built at Cardiff, with the frames constructed at Port Augusta, and the bogie frames at Kelso.
Variations by Class
SCT class
The SCT class are used by SCT Logistics on their freight services from Adelaide to Melbourne, Parkes and Perth. Locomotive SCT007 is named Geoff Smith after the CEO of the company. The benefits of AC traction has enabled a fleet of 15 locomotive to do the work of 20 DC traction equipped locomotives, three AC vs four DC units being needed on the Melbourne to Adelaide journey, and two AC vs three DC units between Adelaide to Perth. An on-train refuelling system carries 50,000 litres of diesel in a tanker behind the locomotives and eliminates the need to refuel en route. SCT's 001, 002, 006 & 013 have been overhauled and repainted during 2019.
LDP class
The LDP class were built by Downer EDI Rail to be leased out to rail operators through their subsidiary Locomotive Demand Power. In December 2008 it was announced that QR National has signed a five-year deal for the nine locomotives, covering the construction and delivery of the locomotives, maintenance, the provision of spare parts, and options to extend the lease for an additional five years. The locomotives LDP001-005 are leased by SCT logistics and used on their intermodal services. They are used on standard gauge intermodal freight services, LDP001-003 were painted in a blue and white Downer EDI Rail livery, while the remainder are in QR National yellow livery. LDP005 is now painted in Progress Rail livery. LDP004 is in white undercoat. A further five were manufactured in 2013.
TT class
With the aging of the 48 and PL-class fleets, Pacific National purchased 31 TT classes for the trains of the Hunter Valley. TT02 was later named "Darrell Sherry". They are equipped with ECP brakes and are used with NHDH, NHEH and NHYH hoppers. They are different in some respects from SCT / LDP category units because they can run at two different weights: their weight, fuel load and operating range when the weight is between 139 and 132 tons Heavyweight same 90 classes; but under 132 tons, they are cleared for normal operation, such as SCT / LDP class. The first locomotives were originally intended to built as LDP010-LDP018, and leased to other railway operators, until Downer EDI and Pacific National reached an agreement to sell directly. TT01 conducted the first test on 26 November 2009. TT130, TT131 and TT132 are owned by Pacific National
WH class
The three WH class locomotives were ordered by Whitehaven Coal entering service painted blue and white. They are used to haul coal trains from Whitehaven's mines in the Gunnedah Basin and are operated by Pacific National.
GWA & GWB Class
In early 2011 Genesee & Wyoming Australia ordered seven locomotives for the Adelaide–Darwin railway. The locomotives are used on several Grain services throughout South Australia and Genesee & Wyoming’s Intermodal services between Adelaide and Darwin. The GWA Class are soon to be accompanied by three, newly commissioned GWB Class Locomotives. They are currently undergoing testing and will enter revenue service when deemed viable. The GWB class have been recently obtained by Genesee & Wyoming Australia from storage in America. The locomotives will be numbered GWB101-GWB103 and will be utilised on Intermodal traffic.
SSR Class
The 2 class members were ordered by Southern Shorthaul Railroad in 2014 to operate its grain services, displacing hired motive power.
