The locomotives were extremely versatile, and the AB class were used on almost every section of the NZR network, the exception being the Nelson Section (closed 1955). In later years, the class were displaced from their mainline duties first by the larger J and K series locomotives, and later by the arrival of diesel locomotives (DA and DG classes in the North Island,DH and DJ classes in the South Island). As a result of the arrival of new diesel locomotives in the North Island from 1955 onwards, many of the North Island-based locomotives were transferred to the South Island to see out their remaining working lives.