California's Railroad to the U.S. 1861 - 1996

Krauss-Maffei ML-4000

18 units delivered

+3 exDRGW units

Original numbers - Prototype Units (cab units)
SP unitsDRGW units
9000 9001 9002 9021 9022 9023
9000 9001 9002 9021 9022 9023
9000 9001 9002 9021 9022 9023
Original numbers - Series Units (SP Hood units)
9003 9004 9005 9006 9007 9008 9009 9010 9011 9012
9013 9014 9015 9016 9017

1965 numbers
9100 9101 9102 9103 9104 9105
9106 9107 9108 9109 9110 9111 9112 9113 9114 9115
9116 9117 9118 9119 9120

This is a condensed history, the best work so far* would have to be SP Historic Diesels Vol.2 - Diesel-Hydraulic Locomotives - by Joe Strapac. Although this book may be a little difficult to find now, I would urge you to chase a copy of this book, for it contains the full history and drama of these important locomotives. (*See Southern Pacific & The KM Hydraulics, published 2014.)

In 1959 UP advertised it would shortly receive 2000hp GP9's, these were being rebuilt by EMD with the then new turbo-supercharging system. These would evolve into the GP20 and SD24, but for the moment SP had nothing that would compare with this, and so was embarrassed...

By 1958 technology had reached its limits, and SP was having to put more and more locomotives on a train to move it at the speed they needed to compete. Although the 2400hp Train Masters were of higher horsepower, they had problems which did not make them suitable for general freight service.

After much research, SP decided to join Denver & Rio Grande Western to go offshore and get Krauss-Maffei of Germany to build six 'Prototype' 4000hp carbody-style diesel-hydraulic locomotives, three for each railroad. A number of modifications were required once operating experience on mountain lines was had, and the three DRGW units found themselves in SP ownership by early 1964.

The SP KM's were delivered in standard Red/Gray paint, the DRGW units were delivered in the yellow/silver/black paint scheme. When they were bought by SP, the exDRGW units had black SP road name and numbers added and were renumbered after the hood units.

When all units were renumbered in "the great renumbering of" 1965, the exDRGW units were placed back in build order between the two types.

The first order was successful enough, for SP to go back to Krauss- Maffei and ordered another 15 incorporating upgrades developed with the six Prototype Units, and built with more American-sourced parts to the more contemporary 'roadswitcher' hood-style configuration. 9001 is an example of the 'Prototype Units' and 9014 an example of the 'Series Units.'

As mountain operating experiences were less than desirable, these units soon found themselves as 'flatlanders'. Eventually the usual practice was to operate one KM with another unit, often an F7A or B, a GP9, or an Alco Century Series.

US locomotive technology finally caught up with these units, and all were scrapped between 1967 and 1968, except for #9113 which was rebuilt to a Simulator Camera Car.

Page updated Jan 2016 with corrections from Robert J. Zenk


  • Southern Pacific & The KM Hydraulics - by Robert J. Zenk, published 2014 by SPH&TS, 304 pages hardcover
  • SP Historic Diesels Vol.2 - Diesel-Hydraulic Locomotives - by Joe Strapac.
  • 1976 Roster part 6 - Extra 2200 South - Issue 59 Jan/Feb/Mar 1977
  • Southern Pacific Historical & Technical Society "Trainline" Fall 2005 No.85 - "A K-M Postscript"

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