Withdrawal of the Wb class.

Cascading effects of dieselisation and electrification

The early 1950's signaled changing times on New Zealand Railways. The last steam locomotives were being built at Hillside Workshops, Dunedin. Wellington's extensive suburban network was largely electrified. An influx of mainline diesel-electric locomotives were imported from English Electric and General Motors. These events sparked a cascading effect, shuffling redundant locomotive power southwards through New Zealand.

Westport received a number of Ww class 4-6-4 tank engines of World War I vintage, surplus from suburban Auckland and Wellington. New, higher-mounted boilers were fitted, giving the locomotives a new lease of life. Despite their modest 65 ton weight, the axleloads were in excess of that permitted on the line through to Westport, and had to be towed through with empty boiler, tanks and bunker.

Final days

Increased numbers of Ww class at Westport had the effect of confining the remaining Wb class to the fifteen miles of branchline through to Granity and Ngakawau, the short return run up the Buller Gorge to Te Kuha and Cascade, and the Conns Creek branch which serviced the Denniston Incline. The Wb class had a limited range due to the modest capacity of the coal bunker, further handicapped by their advancing years.

Wb 298 and 300 were withdrawn from service in October 1955. Wb 292 and 299 lasted a little longer shunting at Westport, rarely venturing out onto the mainline. Late in 1956 they too were withdrawn from service, written off in 1957.

• Wb 300 was towed south to Dunedin for scrapping,
• Wb 298 was broken up at Westport, the boiler eventually dumped at Omoto, near Greymouth,
• Wb 292 and 299 were towed north of Westport to Seddonville, dumped as river protection for the railway formation.