In 1966, the company restructured the Unimog range. The small Mercedes-Benz Unimog U 34 was joined by the medium-heavy 406 series with the U 70 model which, at a later stage, developed into the U 80 and U 84 as engine output increased – figures relating to engine output in hp in each case. Parallel to this, Daimler-Benz introduced the 416 series with 2900 millimetre wheelbase corresponding to the Unimog S. The series initially consisted of the U 80 which developed over the years into U 90, U 100 and finally into the powerful U 110.
In addition, Daimler-Benz introduced the lightweight 421/403 series, complemented at a later stage by the 413 series, to fill the gap between the original Unimog and the medium-heavy series. These new series differed in terms of their wheelbase lengths and their engines which were adopted from the car range (421 series/U 40 with 2.2 litres displacement) as well as from the commercial vehicle range (403 series/U 54 with 3.8 litres displacement). The output ratings of these models likewise rose continuously until the renewal of the range in 1977.