2100 class was first introduced into service in 1970. They were built by Clyde Engineering/Comeng at Rocklea. The 2100s have been the only locos in Qld that have been fitted with 16 cylinder EMD 645E engines.

The 2100 class was the mainstay of QR’s coal haulage from the opening of the Bowen Basin lines through to electrification. After the electrification, they were placed into general freight traffic as well as the remaining non-electrified coal lines. The 2100s are now based all around the state.

The 2100 Class is, in fact, made up of several different classes of locomotives. As each new coal mine was planned, a new batch of locos was ordered. The 2100, 2130, 2150 and 2170 classes were ordered for the Goonyella/Peak Downs, Saraji, Norwich Park, German Creek/Oaky Creek/Blair Athol mines respectively. The 2141 class (initially the 2200 class) was used for the Greenvale nickel mine.

During the late 80s and right through to the present day, a number of the 2100s have been modified. Modifications include lightening of the loco by fitting a smaller fuel tank (A suffix), DOO cab modification which lowers the nose of the loco, adds a larger windscreen for the driver etc. (D suffix). Most DOO modified “A” suffix locos have also had auxillary fuel tanks added, resulting in an “F” suffix. The more recent modifications to the 2100s (namely the 2170s) have seen the addition of a maxi-cab, similar to the 2300s.

Due to the age of the class and introduction of the 2800 and 4000 class, many have been displaced or withdrawn from service. Ten of the original members of the 2100 class have been shipped overseas to Chile. During 2007, six 2100 were sent to EDI Port Lincoln workshops for overhaul/refurbishment for duties with ARG in Western Australia, where they will be known as the DD Class. 2105D was the first loco treated, emerging as DD2356 in early October 2007.

A number of recent maxi-overhauls include the fitting of larger fuel tanks and the fitting of ZTR traction control system. The entire 2130 Class and all but one of the 2141 Class were converted to 2250 Class locomotives between 2005 and 2007.