Constructed between January 1943 and November 1949, the 30 locomotives in the class were designed to haul express passenger services throughout New South Wales.

The 38 class were first conceived in the 1930s when the NSWGR established there was a need for a locomotive to eliminate the complications of double heading on a number of fast intrastate passenger trains.

[3] The conditions of trackwork with frequent sharp curvature to be traversed at high speed would require six-coupled driving wheels in a 'Pacific' 4-6-2 configuration.

[3] Similarly to the earlier D57 class (which had some input from Young), the massively proportioned locomotive incorporated a cast steel chassis.

[4] They suffered many delays during construction, mostly due to resource shortages caused by World War II and the Great Depression.

[8] The 38 class briefly returned to the former Melbourne Limited Express route in April 1962, when 3830 and 3813 hauled the inaugural standard gauge Spirit of Progress from Albury to Sydney.

[5][7] In August 1970, 3801 hauled the Western Endeavour to Perth following the conversion to standard gauge of the Sydney–Perth rail corridor with 3813 assisting as far as Port Pirie.

Components such as the wheels, cab and smokebox were stored in S trucks at Thirlmere, the frame and tender at Clyde and the boiler at Castle Hill until they were donated to the Dorrigo Steam Railway & Museum.