 The South Island allocated locomotives were initially classified DH because they were fitted with adjustable bogies that allowed a higher maximum axle weight and tractive effort The DG and DH axle loading was .By adjusting the spring beams the DH adhesive weight increased to and the tractive effort to .The first regular outing by a DG class locomotive was that of DG 750 in August 1955 when it was sent with 88-seater railcar RM 100, an English Electric DF class locomotive, and a newly arrived Drewry DSB class shunting locomotive to the Wanganui Industrial Fair.