Caption: Canadian Pacific M636 4711 is shown along with 4723 and an unidentifiable sister resting at the former T, H & B Aberdeen Yard in Hamilton. In an attempt to prolong the lifespan of the veteran six-axle MLW fleet, in 1988 CP had M636 4711 rebuilt with a like horsepower Caterpillar 3608 Marine Service prime mover at Peaker Services in Brighton, Michigan. Apparently the new prime mover required considerably more breathing capacity as evidenced by the enlarged and expanded carbody filter arrangement (compared to 4723). Note also the relocated horns and lack of multi-mark emblem at the rear of the hood. While successful, the overall expenditure was considered to be cost prohibitive and no further units were so modified. Nevertheless, the transplant did by her an additional three years of service with CP compared to the rest of big MLW’s which had been displaced by the incoming horde of GE AC4400CW’s. Sold to Minnesota Commercial Railroad in July 1998 and renumbered, the venerable unit continues to soldier on with her replacement power plant. Following a period of storage 71 returned to service in mid-2011. The Caterpillar sound is quite distinct from the original Alco 251 ‘chug, chug, chug’. For a sample of her music go to http://www.youtube.com/watch?v=lBYUcRqIsHE