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Feb 18, 2009
- 1963: Unimog 406, start of the medium-duty series
- 1966: New range structure
- 1972: MB-trac – new approach to agricultural tractors
- 1974: The U 120 introduces the heavy-duty series
- 1976: Range expansion and new designations
- 1985: Start of the new 407 – 437 series
In the early sixties, the small basic Unimog alone was no longer capable of meeting the growing demands and covering the ever more diversified range of assignments. The Unimog S, first and foremost a military vehicle, was not always the right alternative for civilian applications, even though it was available in finishes other than olive green. Therefore, the company launched a medium-duty series with the designation 406 in 1963. The wheelbase of this new, additional Mercedes-Benz Unimog was 2380 millimetres long.
Opening up new dimensions: the 406 series
At the same time, larger diesel engines were for the first time installed under the Unimog's short bonnet: 65 hp generated from four cylinders and a little later even from the legendary, large-volume OM 312 six-cylinder diesel engine with a displacement of 5.7 litres – setting a new standard in performance. With reference to its hp rating, the new Unimog became known as the U 65. With the additional 406 series, Daimler-Benz complemented the Unimog range by a genuine jack-of-all-trades for use on and off the road, permitting completely new applications, for instance as a versatile tractor.
406 series rapidly joined by additional model series
In 1966, the company restructured the Unimog range. The small Mercedes-Benz Unimog U 34 was joined by the medium-duty 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-duty 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 litre displacement) as well as from the commercial vehicle range (403 series/U 54 with 3.8 litre displacement). The output ratings of these models, too, rose continuously until the renewal of the range in 1977.
Unimog complemented by a specialist farm tractor: the MB-trac
This rapid progress in model policy, which may not have been easily comprehensible at all times, resulted in another anniversary: production of the 100,000th Unimog in May 1966. During its career over almost 20 years, the Unimog had developed magnificently ever since the days the first chassis prototype had been completed. It had long since acquired a legendary offroader reputation throughout the world. As successful as the Unimog may have been, it was only rarely used in agriculture. To cover this market segment, Daimler-Benz therefore launched an additional vehicle in 1972: the MB-trac.
The new agricultural tractor combined Unimog engineering, including all-wheel drive and power transmission to four equal-sized wheels, with the looks of a tractor: a long and very narrow bonnet and behind it an angular, high-rising driver's cab. Contrary to conventional tractors, however, the cab was located between the axles and fully enclosed.
Within just a few years, the initial MB-trac 65 and MB-trac 70 (later 700) models developed into a broad series right up to the extremely powerful MB-trac 1500. In spite of this, the MB-trac failed to become a great hit. Daimler-Benz eventually integrated the MB-trac in a joint venture with the agricultural machinery unit of Deutz. Production of the MB-trac was discontinued in 1991.
425 series: the new, big Unimog
The next new Unimog series emerged in 1974, two years after the MB-trac. Large-scale production began in 1975: the U 120 from the 425 series was the heavy-duty top model in the range of versatile tractors and working machines from Daimler-Benz. Its conspicuous features included a new, angular cab and a large bonnet set at a flat angle. The latter ended in a large-surfaced, black radiator grille. This cab design has basically remained unchanged for the last 25 years.
The 425 series initially included a 120 hp model (boosted shortly afterwards to 125 hp in the U 125) with 2810 millimetre wheelbase and a permissible gross weight of nine tonnes. Also in 1975, production of the 435 series as the successor to the Unimog S began for the German armed forces; these vehicles had wheelbase lengths of 3250, 3700 or even 3850 millimetres. From 1976, the 424 series fitted into the range somewhat further down below.
New model designations to create a clear structure
At about the same time, Daimler-Benz introduced new model designations. The models with the rounded, meanwhile classic shapes were the Mercedes-Benz Unimog U 600/L, U 800/L, U 900 and U 1100/L. New angular shapes were the hallmark of the Unimog U 1000, U 1300/L, U 1500 and the flagship, the U 1700/L with 124 kW (168 hp) engine. The letter "L" indicated the long-wheelbase version – the majority of models were meanwhile available in two wheelbase lengths.
The Unimogs with rounded cabs belonged to the lightweight series, the new models with angular cabs made up the medium-duty and heavy-duty series, the division being made on the grounds of permissible gross weight. Several engines were available for different series – the Unimog designation system was not easy to understand. And finally, the range was still complemented, though in declining numbers, by the tried-and-tested Unimog S, the only one with a petrol engine.
Disc brakes in Unimogs long before their introduction in trucks
Clearly more easily understandable were the technical highlights: with the exception of the bottom-of-the-range model, all Mercedes-Benz Unimogs were fitted with disc brakes all round at the time the new model designations were introduced – long before this safety equipment became state of the art in trucks. The efforts of the Unimog people to give every customer the model he or she needed paid off in the form of another record figure: in 1977, the 200,000th Unimog was produced.
Complete renewal with the 407, 417 and 427 series
In the following years, the Unimog range remained largely constant. But then, between 1985 and 1988, new models were again launched one after the other: Daimler-Benz completely replaced the entire range by the 407, 417, 427 and 437 series. The cab from the medium-duty and heavy-duty series was now also used for the lightweight models. New wheelbase lengths, dimensions, weights, chassis and engines under the cabs' sheet metal skins resulted in completely new vehicles.
After this renewal, the range was larger than ever before, extending from the lightweight, particularly easily manoeuvrable Mercedes-Benz Unimog U 600 with an output of 44 kW (60 hp) and a gross weight of 4.5 tonnes via countless versions – the result of further expansion in the early nineties – to the three-axle U 2400. Its engine developed a new record output of 177 kW (240 hp) from a displacement of six litres. The two-axle version's permissible gross weight was 14 tonnes.
Output increased almost tenfold since the beginning
From 1993, the range was rounded off at the top end by the Unimog U 2450 L 6x6, a three-axle unit with all-wheel drive. The people who had developed the first Unimog more than 40 years earlier would certainly not have dared dreaming of such models – if anything, a comparison of engine output is worth its while: from the first Unimog to the new top model, it had increased almost tenfold.