also made them unsuitable for the NIMT. The G class were mostly based at Ohakune and operated between Taihape and Ohakune on the NIMT. The central section of the NIMT of 93 miles (153 km) from Taumarunui to Taihape had been relaid with heavier 70 lb/yd (34.8 kg/m) rather than 53 lb/yd (26.3 kg/m) rails in 1901 for the introduction of the heavier NZR X class locomotives. Withdrawal Trainloads were reduced and this defeated the purpose for which the Garratts were purchased – namely to operate heavy loads over a vital mainline section of the NIMT route, the central section including the Raurimu Spiral. The trailing engine axle under the cab carried a heavier load than the leading engine trailing axle and experienced continual problems with overheating. Also, the coal bunker carried insufficient fuel in-service and this problem was never remedied because it would have increased the axle loads beyond the light track capabilities. In 1937 the engines were withdrawn from service. Their numerous design faults sealed the fate of these locomotives when the K class was introduced in 1932. Rebuilding as Pacifics Due to the troubles faced with the Garratts in their original form, a proposal was put forward in late 1935 for the three Garratts to be dismantled and the engine units used to build six new 4-6-2 tender locomotives. The three locomotives were dismantled at Hutt Workshops in 1936 and the engine units shipped to Hillside Workshops in Dunedin for eventual rebuilding. The engines as rebuilt were fitted with a new third cylinder, a modified AB class boiler, a new cab and trailing truck based on those used on the Baldwin AA class, and a new Vanderbilt tender based on those used on the AB class, but of welded construction and fitted with roller bearing bogies. The original plate frames were retained as was the Gresley conjugated valve gear. In service The first rebuilt locomotive, G 96, was outshopped on 8 September 1937 and dispatched north after initial tests to Christchurch for use on the Midland line. Some minor adjustments were required although the performance of the initial rebuild was deemed satisfactory and the other five engine units were subsequently rebuilt with the last locomotive, G 100, outshopped on 4 March 1938. The rebuilt locomotives were largely used between the Arthur's Pass and Christchurch section of the Midland line on heavy coal haulage during the Second World