The N&W shops in Roanoke, Virginia gave all Y Class engine and tender axles roller bearings and they used the same outside frame lead truck as the Class A. The trailing truck was also equipped with roller bearings which were fit into an outside frame design. With these improvements the Y6s cost considerably more than their earlier brethren, but just as the maintenance records show, these locomotives had a time available for assignment rating far superior to any of the predecessors.

The Y6b had a starting tractive effort in simple configuration of 152,206 pounds. While in the compound mode, a tractive effort of 126,838 was achieved. These locomotives delivered 5,500 horsepower, a substantial bit of power indeed. The Y6b locomotive engine weight was 582,900 pounds with 522,850 pounds directly on the drivers.

When the N&W ceased their mainline steam operations in the summer of 1959, 50 of the Y6s were still running out serviceable miles in the coal fields waiting for the final order of diesels to replace them. The last of the Class Ys were retired in the summer of 1960.