In order to reduce the axle load of the trailing axle of the D50 class with a 2-8-2 wheel arrangement, a two-axle bogie was installed in its place from 1951. Along with other modifications, the D60 class was created. The D51 class was converted into the D61 class and the D52 class into the D62 class in the same way. In addition, the cylinder diameter had been reduced from 570 to 550 mm to reduce the tendency to slip. The locomotives were retired between 1966 and 1974. Four have survived to this day. 