When the trains became heavier and heavier, the NZR developed a powerful shunting locomotive as a tender locomotive. In order to keep the axle load low and to enable sufficiently large driving wheels for occasional use in front of passenger trains, the class WF 2-6-4T tank locomotive was used as the basis and the second trailing axle was removed. After the class C had become too light for the ever heavier trains, it was also used for suburban trains. Half of the locomotives were retired between 1964 and 1968. 