In 1961, IH introduced two small new models: the 404 and the 504. A standard three-point hitch was now a factory feature, and it was equipped with a push-arm sensing mechanism. A significant innovation in the tractor world was the hydrostatic steering offered as an option for the 504. Also new for tractors was a dry paper air filter. There was a cooler for the hydraulic oil. The engine in the 404 was the same 2.2-liter gasoline engine previously used in the 340 model. The larger 504 was only a few horsepower more powerful but was also available as a diesel. The 504 also featured a larger-series transmission with a high-speed gear option. A bit later, the 6-cylinder 606 was introduced, which was only available as an International version with a wide front axle.

In 1965, the more powerful 656 was introduced, and two years later, the long-developed 656 Hydro with hydrostatic transmission went into production. The speed could be adjusted (0...34 km/h), and the driving direction could be changed with a single lever.

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