As part of the D&H South electrification scheme the Portland Shops designed an express motor to run freight at 110+ MPH (class 6 trackage for 110mph/177kph, and some Canadian trackage that was temporarily waivered for 150mph/250kph.)

The solitary class L – #799 – is what came out of it; a motor that drew on 5 years of testing of regeared class E & K motors, actually capable of pulling (short) freights at 150mph without catastrophe.

The big change from the class K design that was giving it a pilot truck to cut down on an alarming leading truck shimmy at speeds over 130mph; that plus the appropriately huge AC transformer it needed for operation on D&H South stretched the carbody out to an unheard of 75' – long enough so that the rear end needed to be tapered so it could remain within Amtrak’s NE Corridor clearance envelope.

Alas, Amtrak balked at the idea of running super-fast freights on the NE Corridor, so 799 was the only unit of this class built.

#799 operated as delivered for about 12 years, then went into the shops to be rebuilt as a slower-speed (from 250kph down to 160kph) motor. At a lower top speed the pilot truck wasn’t necessary, so Portland replaced the front truck assembly with a single B truck, removed the cab section, and returned it to service as a calf.

As a calf, #799 is used both as a booster unit for freights on the Chicago to St Johns mainline, as well as the motor section of dual-power lashups on through freights from New England to the Ottawa Central’s line to Sault Saint Marie.