WP’s small switch engine fleet made it past
merger day with only one casualty, SW9 604, which was sold to Pielet
Brothers in McCook, Illinois. As it turns out, however, the 604
provided extended life to another historic locomotive as it gave up
its main generator to UP E9A 951 after the E-unit suffered a
generator failure during a California Operation Lifesaver trip. Of
the remaining ex-WP SW9’s, only one other was vacated, WP 602 was
sold to Western Cooperative Fertilizer in Calgary, Alberta Canada
where it replaced an aging ALCo as a plant switcher. The other four
SW9’s were all sent through UP’s Omaha shop and rebuilt into SW10’s.
The original SW10 rebuild program on the UP began in 1980 after two years of development work by the Mechanical Department. Three of EMD’s switcher models had been chosen for the program , the SW7, SW9, and TR5A, since all were similar in most details and were powered with 567B or BC engines which could economically be overhauled and upgraded to 12-645C engines using new 645 power assemblies in place of the original 567 assemblies.
Included in the rebuild were all new electrical cabling and wiring, updated electrical gear, including some module cards with solid state circuitry. A new consolidated equipment rack for the water tank, oil filters, and other mechanical components was built using parts from retired GP9s. A new radiator section using twin 36-inch electrically-powered cooling fans was also taken from retired GP9s and installed thus replacing the expensive to maintain and inefficient belt-driven 54-inch fan originally equipped in these units. The new design also included a new large sandbox which was in front of the hood in place of the original radiator fan intake and shutter assembly. This new sand box design did away with the two original internal sand boxes. The cab interior layout and design also received attention including a modern control stand, electric cab heating, an electric refrigerator, and other features which brought it up to the FRA-mandated "clean cab" standards. The original friction bearing trucks were rebuilt and converted to roller bearings.
With the completion of UP 1274 (ex-WP SW9 606) on December 30th, 1984 the SW10 rebuild program came to an end.