The SL Gunma Minakami and the SL Gunma Yokokawa are powerful trains that travel through the wild country of Gunma thanks to the D51 498 and the C61 20 steam locomotives.
The D51 498 was originally used for pulling freight cars, and the C61 20 was built as a locomotive for pulling passenger cars. Because they were designed for different purposes, the drive wheels are different in size and number.
The D51 498 has four smaller drive wheel axles, and the C61 20 has three larger wheel axles. When the drive wheels are small, the train gains in ability to handle hills, and when the drive wheels are large, the ride is more comfortable with less vibration. When you ride the trains, you will probably be able to tell the difference. Try them both out and compare.