The Northern Explorer runs 3 times a week in each direction and takes about 11 hours for the 680 Km (420 miles) between Auckland and the capital. The DF class was introduced from 1979 and in 1990's rebuilt to EMD GT22MC reclassified DFT and later DFB with the current rebuilding program which includes Brightstar for those not already with it. The train was built at Hillside workshops in Dunedin and won a design award.
http://trainspo.com/photo/51873/?list=class