2-8-8-4 wheels. The locomotive's superstructure was attached to the rear group, while the forward group and leading truck could swing laterally on curves. All Yellowstones had fairly small drivers of . (For greater speeds, the Union Pacific Railroad chose a four-wheel leading truck and drivers of for its Big Boy 4-8-8-4 class.) Several classes of Yellowstone, especially the Duluth, Missabe and Iron Range's locomotives, are among the largest steam locomotives, with the exact ranking depending on the criteria used. The Northern Pacific Railway was the first railroad to order a 2-8-8-4. The first was built in 1928 by American Locomotive Company;
2-8-8-8-8-8-2 2-8-8-8-8-8-2 Under the Whyte notation for the classification of steam locomotives, a 2-8-8-8-8-8-2 has two leading wheels, five sets of eight driving wheels, and two trailing wheels. Because of its length, such a locomotive must be an articulated locomotive. It is not longer than a normal articulated; the fourth and fifth sets of drivers are located under the tender. Other equivalent classifications are: UIC classification: 1-D-D-D-D-D-1 (also known as German classification and Italian classification) AAR classification: 1-D-D-D-D-D-1 French classification: 140+040+040+040+041 Turkish classification: 45+44+44+44+45 Swiss classification: 4/5+4/4+4/4+4/4+4/5 The equivalent UIC classification is to be refined to (1'D)DDD(D1'). The Baldwin Locomotive Works