Based on the success of the L-3 Mohawks, the New York Central designed a faster variant that was designated L-4. It had the same boiler, but drivers which were 72 instead of 69 inches and cylinders with a diameter that was half an inch greater. They now also got roller bearings on the drivers. Despite their higher top speed, they were also used for both passenger and freight trains.
In 1942 and 1943, two batches of 25 each were built as L-4a and L-4b. A tender with a coal capacity of 42.5 tons was enough to cover half the distance from New York City to Chicago without refueling. The 15,500 gallons of water were replenished at track pans while running. The tender of the L-4b was only minimally smaller. They were retired between 1954 and 1957. 