PIKO HO 97454 D&RGW KM ML4000 4002 As-Delivered DCC Sound

The prototype:
In the early 1960s, American railroad companies D&RGW and SP were looking for more
powerful diesel locomotives to haul heavy freight trains on their lines traversing the
Rocky Mountains and the Sierra Nevada.
Current units from EMD did not meet what SP and Rio Grande were looking for, so both
railroads approached Germany’s Krauss-Maffei about building high-horsepower diesel-hydraulic locomotives. Krauss-Maffei answered the call with their ML4000 diesel-hydraulic locomotives. Hydraulic power transmission, which was not common in the US, not only provided the required power but enabled better traction and a higher power-to-weight ratio.

With a rated output of 4000 hp, the six-axle ML 4000s were the most powerful single-frame diesel locomotives of their time. The D&RGW and the SP initially ordered three
engines apiece, which were exported to the USA in 1961. While still making frequent
modifications to these initial „Prototype“ units, SP placed an order with KM in 1963 for 15 mechanically similar but very different looking „Series“ units. The Rio Grande units were sold to the SP in 1964. Southern Pacific’s KraussMaffei units remained in service until 1968.