Great Northern Y-1a #5011, which I mentioned above, was an odd beast.
GN electrified the original Cascade Tunnel (approximately 1.5 miles north and 500 feet higher than today's tunnel) in 1909, just twelve years after opening the tunnel. The first Cascade Tunnel electrification ran between Cascade Tunnel station on the east, and Wellington on the west, just 4 miles of track. It was a unique, one-of-a-kind three 6600V three phase AC system, which would run at either 15 or 7 mph depending on which set of induction windings you tapped. The little electrics each had two trolley poles, and the rails acted as the third phase. GN used four Alco-GE boxcab electrics, rated at 1500hp and weighing 115 tones, with three locomotives coupled together and hauling trains at a constant speed of 15.6 mph. When larger trains required four locomotives the motors were concatenated and speed was halved to 7.8 mph to avoid overloading the power supply.
The original Cascade Tunnel route was plagued with snow slides and a stiff grade, so in 1927, GN began constructing the modern day tunnel, farther south and at a lower elevation. The ruling grade was still 2.2 percent, but 21 miles of 2 percent or worse grade was eliminated, the line length was reduced by 8.7 miles, and maximum elevation was lowered by 502 feet from 3,382 feet to 2,881 feet. They also decided to upgrade to a more standard electrification and purchase new, bigger power. Alco-GE constructed 8 boxcab Y-1 electrics over a period of 4 years, two in '27, two in '28, and 4 in '30. The Y-1s operated on single-phase 11 kilovolt, 25 Hertz AC, and generated 3000 continuous horsepower, with a 1 hour peak of 3300hp, on a 1-C+C-1 wheel arrangement.

One of those Y-1s, the #5011, was involved in an accident at Tonga, Washington in July of 1945. During the rebuild, for whatever reasons, GN had brand-new (and expensive) FT cabs from EMD installed on both ends of the unit and reclassed it to a Y-1a. I have to wonder if this was maybe a pilot for a planned rebuild program that would have been performed on all Y-1as, only for it to be stillborn due to rise of the diesels making the electric power redundant. The boxy enclosure over the headlight contained a bus bar that allowed multiple Y-1s to share power from only a single pantograph, reducing catenary wear.

The eight Y-1s all lasted until de-electrification in 1956, when they were put out to pasture with the Alco-GE W-1s and Westinghouse Z-1s. The PRR sent a team of employees out to the GN in in August of 1956 and they inspected the 15 available GN electrics, but decided to only take the 8 Y-1s. They were cheap, available electrical power, and they used the same voltage and frequency, so major mechanical changes would be minimal to make them operable on the PRR. They were shipped east and the Y-1a, #5011, was chosen to be broken up for parts for the oher seven Y-1s, as well as to use the EMD FT cabs on a couple of wrecked PRR F-units (going back to earlier discussions on cost and complexity of F-unit noses). There were 48 mechanical, structural and electrical changes made on the remaining 7 before they went into service on the Pennsy. Among the changes was the removal of the rooftop bus connectors and regenerative braking, and addition of PRR-type MU connections, US&S cab signals and electric water coolers. The other noticeable difference the Pennsy made was to remove the side doors and grab irons to meet clearance restrictions.
Reclassed to FF2s, they were not particularly successful on the PRR. The big issue was that GN used them in basically a mountain helper district, and so they never operated very fast. Between that, and their age, they were equipped with solid bearings, and when PRR tried to operate them at 50mph mainline freight speeds, they tended to overheat axle bearings. Sustained speeds had to be kept below 30mph, which made them a rolling traffic jam on the PRR mainline. Also, the FF2's had to be operated very carefully when applying power from standing stop to prevent the wheels from breaking loose from the flanged tire rims and dropping the whole chassis onto the roadbed. Used mainly in helper service at Columbia and Thorndale, they began to be retired as early as 1960, and the arrival of the E44s polished off the FF2s, along with the experimental one-off Westinghouse E2/E3s, the remaining P5 fleet and all the other one-off or older classes outside of the single DD-1 pair, two O-1s and two L-6s in Manhattan tunnel maintenance and transfer service.
