The class DH was a diesel-hydraulic shunting locomotive built between 1966 and 1974 by Walkers in Australia. All 73 locomotives initially came to QR and were also used for light short-haul freight trains. With a 470-hp Caterpillar engine and a Voith transmission, they weighed only 37 tonnes. With the closure of many freight yards in the eighties, withdrawals started when the oldest locomotives were only around 20 years old. By the early nineties, most were already out of regular service with QR.

After that, many were sold to other operators and were re-gauged to smaller gauges thanks to their low axle load. 29 came to sugar mills in Queensland and now operate on two-foot narrow gauge lines. Others were rebuilt to 2 ft 6 in (762 mm) or 900 mm. Some are operating on heritage lines where they are being used as a replacement for steam locomotives in times of high fire risk. 15 came to either Vietnam or Malaysia where they are operating under metre gauge.