The GN numbered the units 5010–5017 and classified them Y-1. After being involved in a wreck at Tonga, Washington in July 1945, the 5011 was rebuilt with a streamlined appearance and EMD F-unit cabs; the GN reclassified it as Y-1a.
In 1956, the GN dieselized operations through the Cascade Tunnel. The electrical system was decommissioned, and the Y-1 locomotives were sold to the Pennsylvania Railroad, who classified them as FF2. GN 5011 was broken up for spares, and the remaining seven locomotives were overhauled and converted to PRR standards and then placed into service, being assigned numbers 1–7 on the PRR. The lasted a few more years on the PRR, and were all scrapped between 1957 and 1966.
Keyes, Norman C, Jr.; Middleton, Kenneth R. (Autumn 1980). "The Great Northern Railway Company: All-Time Locomotive Roster, 1861–1970". Railroad History. Boston, MA: The Railway and Locomotive Historical Society, Inc. (143): 117. ISSN0090-7847.
Pennsylvania Railroad. "FF2". PRR Locomotive Diagrams. Retrieved 2006-01-05. (simple drawing and specifications, for general reference by railroad staff).