Models 383, 423, and 453 were replaced in 1975 by the 433, 533, and 633. These models formed the simplest lineup of the German and French IH production, the so-called A-family. The most important innovation compared to the predecessors was the new synchronized transmission. The hydraulics were also improved and enhanced. In 1980 and 1981, the lineup was expanded upwards with models 733 and 833. At the same time, the Silent 85 cab, manufactured by the French company Timmerman, was introduced.

The lineup remained in production as a further developed, inexpensive basic tractor until the 1990s. In 1985, the brand naturally changed to Case IH, in 1987 the cab was renewed, and in 1989 production moved to England, after which the 33 series was replaced by the 40 series.

Only model 533 of the 33 series was imported to Finland between 1975 and 1977, equipped with the Turla cab, as smaller IH models were mostly imported to Finland from England. The technical data in the table correspond to the earlier models.

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