ALCO Century 636
The ALCo Century 636 was the most powerful single-engine diesel-electric locomotive constructed by the American Locomotive Company. It used their 251 prime mover. The locomotive had a C-C wheel arrangement and. The locomotive rode on a pair of trucks of all-new design, known as the Hi-Ad, standing for 'high adhesion'. Visually, it is similar to the Century 630, but can be distinguished by the intercooler box. The C630 has two grilles on the intercooler box, one above the other, whereas the C636 only has the upper grille.
Production
Between 1967 and 1968, 34 C636 locomotives were built by Alco in Schenectady, New York. Despite many new and innovative features, the C636 could not hold its own in the marketplace. Three demonstrator locomotives were built costing Alco about $5.5 million. Problems with Alco demonstrator number 636-2, the only demonstrator locomotive operating, were a factor in dissuading potential customers. During an evaluation on the Santa Fe Railway, the same traction motor blower on 636-2 failed and was replaced on three of four runs. Unit 636-2 also had unsatisfactory results while being tested on the Southern Pacific Railroad.Montreal Locomotive Works produced the MLW M-636 variant of the C636 for Canadian Pacific Railway and Canadian National Railway.
In Australia, AE Goodwin built 29 C636s between May 1968 and September 1970 for Pilbara iron ore railroads. Hamersley Iron purchased 12 units in 5 separate orders. Bechtel purchased 5 C636s for use in the construction of the Mount Newman Mining facilities. The latter company ordered 12 C636s a year later and bought Bechtel's locomotives. Hamersley Iron had their fleet rebuilt in the 1980s by Comeng, Bassendean with the Australian designed Pilbara cab.
Original owners
| Railroad | Quantity | Road numbers | Notes |
| Alco Products | 3 | 636-1–636-3 | To Québec Cartier Mining Company 77-79 |
| Illinois Central Railroad | 6 | 1100–1105 | to Illinois Central Gulf in 1972, same numbers |
| Penn Central | 15 | 6330–6344 | Ordered by PRR before PC merger; to Conrail as 6780-6794 |
| Spokane, Portland and Seattle Railway | 10 | 330–335, 340–343 | To Burlington Northern 4360-4369 |
| Hamersley Iron | 12 | 3006–3017 | Built by AE Goodwin, Australia |
| Mount Newman Mining | 17 | 5452–5468 | Built by AE Goodwin, Australia |
| Total | 63 |