As a direct development of locomotive number 5000, ten units were built in 1938, which were given the numbers 5001 to 5010. They differed from their predecessors primarily in the significantly larger driving wheels. These measured 74 inches in diameter and allowed the locomotives to run at up to 70 mph without any problems, although they were actually only intended as freight locomotives. The boilers had a slightly smaller total heating area, but the firebox area was larger and the boiler pressure had been increased from 300 to 310 psi. This resulted in a cylinder output of more than 6,000 hp, which almost compensated for the loss of traction due to the larger wheels.

The cylinders were cast in one piece with the frame, resulting in a single component weighing approximately 87,000 pounds. The first five locomotives got tenders with a lower curb weight, which now held 21,000 gallons of water and 52,000 pounds of coal and still only came loaded to 366,200 pounds. The last five locomotives were oil-fired, with tenders holding 20,000 gallons of water and 7,000 gallons of oil. Another development followed six years later in the form of the class 5011.