The Rewanui Incline was on the West Coast of the South Island, just north of Greymouth. A Fell centre-rail was used for braking purposes only - but quite a lot of gear was sent south from the Rimutaka Incline. W and We class locos, deemed as less successful on the Rimutaka Incline, were the mainstay on the Rewanui, along with Ww locos fitted with centre-rail brakes. Brake vans went south at various stages, particularly after the Rimutaka line closed in 1955. The Rimutaka Incline was between Summit and Cross Creek, some 60km northeast of Wellington on the government's Wairarapa Line - quite distance from and in a different island to the Rewanui Incline. See more about this system at this link:

http://www.rimutaka-incline-railway.org.nz/history/fell-centre-rail.html

Following World War II, North Island coal was in short supply and, as an experiment, K 927 was converted into an oil-burner in October 1945. Results were so successful that all K and Ka locomotives were converted, much to the delight of the firemen. Ka's 958 and 959 were the only 4-8-4's built as oil-burners. In the South Island quality West Coast coal was in good supply, and the six Kb's remained coal burners. In 1953 when the North Island coal was again plentiful and oil prices escalated, K's 901, 915, and 925 were converted back to coal burning, but the engine crews refused to work them. They were converted back to oil in 1954 when oil prices fell.

A total of 71 class K, Ka, and Kb 4-8-4, three and a half foot gauge locomotives were built between 1932 and 1950, most by the Hutt Workshops on the North Island, but six were built at the Hillside Workshops in 1939 for use on the South Island. Retirements and scrapping began in 1964, as the GM G12 diesels began arriving. Five 4-8-4 locomotives were saved from scrapping; the original K number 900, Ka's 935, 942, 945, and Kb 968.

The most outstanding feature of the NIMT (North Island Main Trunk) is the Raurimu Spiral on the central section 25 miles south of Taumarunui. A testing ground for any locomotive, the spiral has one complete circle, three horseshoe curves, and two tunnels, all on an average grade of 1 in 52. Between Raurimu and National Park, southbound trains climb 700 feet in only 7 miles.