In 1953, EMD introduced the SW900 switcher as the successor of the SW8. With the horsepower rating now being a part of the type designation, the 900 stands for an increase of 100 hp compared to the SW8. Additionally, the V8 engine now was the more reliable 567C model instead of the 567B. Between 1953 and 1969, EMD built a total of 260 for US customers and 14 for exports. Some of these had been rebuilt from old Winton-engined switchers and still had the same generator with only 600 or 660 hp. Some were also rebuilt from Baldwin VO-1000 and had 1,000 hp. Additionally, GMD built 97 in Canada for the domestic market.

The SW1200 was introduced only shortly after the SW900 and could be seen as the successor of the SW9. It still had a V12 of the same power as the SW9, but this now also was the new 567C model. EMD built 733 for US customers and 32 for export. Again, GMD built 287 for the Canadian market. Some of these locomotives were specially equipped for service as a road switcher and were called SW1200RS. Changes included flexicoil trucks and larger fuel tanks. Additionally, the SW1200 could be ordered with dynamic brakes.