Unimog: Merc’s all-terrain multi-purpose marvel
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Unimog: Merc’s all-terrain multi-purpose marvel

By MarkOastler - 14 March 2022

There are off-road vehicles - and then there’s the Unimog. While legendary names like Jeep, Land Rover , Land Cruiser, Range Rover and Patrol are synonymous with off-roading, this high-riding Mercedes-Benz stands alone for being designed with the most extreme work and adventure duties in mind.

The Unimog has evolved through nine decades of peerless German engineering and produced a bewildering number of variants, designed to perform a seemingly endless list of specialised roles for a vast number of customers.

Cast an eye across the globe and this go-anywhere workhorse can be found exploring jungles, mountains, deserts and ice-caps, assisting with military, rescue, foreign aid, construction, mining, forestry and railway operations (yes, even railcar shunting), maintaining critical utilities and operating a multitude of implements for digging trenches, drilling post-holes, sawing logs, trimming roadsides, clearing snow from roads and countless other tasks.

The Unimog’s versatility as an all-purpose implement carrier is unmatched.
Image: Mercedes-Benz Group AG.

The Unimog is simply the ultimate off-roader and implement carrier. Proof of its original design excellence is that despite a multitude of variants being developed over the decades, it has adhered to fundamental design principles that its loyal worldwide customer base relies on.

They include a rugged ladder-frame chassis which allows a certain amount of flex at each end that is effectively part of the vehicle’s suspension system. Its short overhangs also provide astounding approach and departure angles.

A forward-control cabin that affords the driver a commanding view of the terrain and implement operation. Modern versions can also ingeniously switch from LHD to RHD in the field, to allow drivers to work on the most convenient side according to their requirements.

Portal axles with angled drop-shafts that allow wheel centres well below the primary axle lines, providing extremely high ground clearance, ramp-over angles and water-fording ability without the need for large tyres.

Extreme off-road ability is a Unimog hallmark. 
Image: Mercedes-Benz Group AG

Premium traction provided by front and rear diff-locks, plus torque tubes that encase the shafts delivering drive to the front and rear axles. These protect the driveshafts, assist in longitudinal axle location and generate downward thrust from torque reaction under power, to optimise vertical tyre loadings and therefore traction.

Coil springs to provide both a smooth ride and outstanding axle articulation, resulting in wheel travel combined with high ground clearance that allows the Unimog to crawl over large obstacles like boulders and fallen trees that would defeat conventional off-roaders.

Unimogs are also designed to operate a vast range of implements, with powerful hydraulic circuits and shaft-drive PTO (Power Take Off) connections.

And the Unimog’s suitability for highway operation means it can return to secure premises overnight rather than be exposed to potential vandalism or theft when parked on remote job sites.

Fact is, there have been so many models and such a mind-boggling number of variants of those models, you’d need a state library to document them all. Instead, we’ve trimmed this broad overview of Unimog history to focus on the most significant models.

Albert Friedrich’s prototype was tiny, but versatile and very capable off-road.
Image: Mercedes-Benz Group AG

First Unimog 1948

The name Unimog is an abbreviation of the term Universal-Motor-Gerät, or universally applicable motorised device, which appeared on early technical drawings before becoming its official name in 1947.

The Unimog was invented by German engineer Albert Friedrich, who during the second world war was head of the aircraft engine design department of Daimler-Benz. At the end of hostilities in 1945, with a defeated Germany in ruins and its population battling food shortages, the unemployed Friedrich identified an acute need for a new type of vehicle that could assist in his homeland’s post-war recovery.

Friedrich’s primary focus was on agricultural use, with the ability to operate numerous farm implements. However, what he envisioned was more off-road capable and versatile than a conventional farm tractor, with all-wheel drive and four wheels of equal diameter for comfortable road use. It’s interesting that Rover in the UK was thinking along broadly similar lines at this time, but the Land Rover that emerged in 1948 was a very different vehicle to the Unimog.

Boehringer Unimogs created customer demand that only Mercedes-Benz could meet.
Image: Mercedes-Benz Group AG

Friedrich first had to convince the US armed forces, which were occupying Germany at the time, that his proposed vehicle was not for military use, as production of any industrial appliance required a manufacturing license issued by the allies.

Having gained this key approval, which prioritised limited supplies of steel and other materials, Friedrich teamed with specialty manufacturer Erhard and Söhne to create a working prototype of his design. In the spring of 1947 Friedrich, fellow engineer Hans Zabel and Erhard and Söhne revealed their Unimog prototype.

It was a tiny front-engine vehicle with a 1720mm wheelbase and just 3.5 metres (3520mm to be exact) in length; its 1680kg kerb weight indicative of robust construction. The 1270mm track width was specifically designed to fit between rows of potatoes. There was a basic cab for driver and passenger with removable canvas roof and sloping front engine cover. Behind this ‘cabrio’ was a sturdy cargo platform designed for carrying loads of up to one tonne.

Its drivetrain comprised a 1.7-litre four-cylinder diesel engine sourced from Mercedes-Benz, with a meagre DIN 25hp (18kW) and 75 ft/lbs (101Nm) being fed through a single-plate clutch and six-speed manual transmission to the rear wheels. A transfer case allowed the driver to switch between rear-wheel drive and four-wheel drive as required and its unique coil-spring portal axle design resulted in a substantial 380mm of ground clearance. There was also a towing hitch and shaft-driven PTOs.

The Unimog first displayed the famous three-pointed star in 1953.
Image: Mercedes-Benz Group AG

The Unimog’s top speed of less than 60km/h seems glacial by today’s standards, but it was faster and more comfortable than a contemporary farm tractor for road use. And its small diesel engine was economical, with frugal 28mpg (10L/100km) consumption welcomed during post-war fuel rationing.

A positive response to the Unimog prototype encouraged Friedrich to commit to volume production. However, Erhard and Söhne, although skilled in hand-built prototyping, was not equipped for the large-scale automotive manufacturing Friedrich was seeking.

German car makers, including Friedrich’s former employer Daimler-Benz, showed no interest in adding the Unimog to their recovering production lines. Well, not yet anyway. This led Friedrich to machine tool manufacturer Boehringer, which commenced production of the Unimog in 1947 in preparation for its official launch at the Frankfurt agricultural show in 1948.

Translation: six forward gears, two reverse gears, three PTO shafts and all-wheel drive. There were also front and rear diff-locks and an optional two-speed crawler gearbox.
Image: Mercedes-Benz Group AG

The new Boehringer Unimog, with its distinctive ox head emblem, exceeded expectations by attracting a full order book. However, this also exposed limitations in the tool maker’s production capacity, which although hand-building around 600 Unimogs could not keep up with soaring demand.

Friedrich also accepted that for the Unimog to realise its potential, it would need the ongoing engineering development and larger dealership network that only a well-established automotive manufacturer could provide.

So, in 1950 Daimler-Benz, already supplying engines and now with tangible evidence of its sales potential, took ownership of Unimog. Production soon commenced at the Mercedes-Benz truck manufacturing plant at Gaggenau, with the first examples rolling off the line in 1951.

The first Unimog, like its successors, showcased quality German engineering. 
Image: Mercedes-Benz Group AG

The first Unimogs manufactured by Boehringer carried the model code 70200, which was renamed 2010 under Mercedes-Benz. Otherwise, the vehicle was largely unchanged during its early years of manufacture at Gaggenau and continued to display the original ox head emblem without Mercedes-Benz identification.

During this time the Boehringer sales outlets were gradually merged with farm tractor sales in the Daimler-Benz sales network, while efficiencies in Unimog production were implemented to increase output, reduce costs and boost sales.

Fully-enclosed ‘frog-eye’ cab option was introduced in 1953. Non-slip 'circular steps' on the front wheels assisted cabin access.
Image: Mercedes-Benz Group AG

In 1953 there was another name change from 2010 to Unimog 401. This effectively became a new Mercedes-Benz model type, validated by the marque’s famous three-pointed star being displayed for the first time. The ox head emblem remained until 1956.

Initially the Unimog 401 was available only with the original cabrio cab, but in late 1953 it was joined by a fully-enclosed variant called the Froschauge (frog-eye) using a cab initially supplied by motorhome manufacturer Westfalia with distinctive protruding headlights. The Unimog was now an all-weather vehicle.

The 401 was also joined by a longer wheelbase alternative called the 402, with a significant 390mm increase in wheelbase offering buyers more load space and body options. In 1956 the utilitarian 401/402 evolved into the 411 series, which with choice of wheelbases, several small power increases, introduction of a full-synchromesh gearbox and other upgrades remained in production until the late 1980s.

Bigger 404 series expanded the Unimog’s appeal, particularly for military use.
Image: Mercedes-Benz Group AG

404 Series

In 1955 a new model joined the Unimog family in the form of the 404 series, or Unimog S. Unlike previous models, the 404 was designed with more than agricultural use in mind.

Its longer 2670mm wheelbase, more powerful diesel and inline six-cylinder petrol engines and higher 1.5-tonne payload capacity, made it suitable for a much wider choice of working roles.

The most prolific buyer of 404s was the Bundeswehr (German military re-established in 1956) along with armed forces from other countries, but it also proved popular in numerous non-military roles particularly as a forest fire-fighting vehicle.

The 404 remained in production from 1955 to 1980, during which time more than 64,000 examples were produced which is the highest production figure of all Unimog models.

Iconic 406 series (note grille opening for PTO shaft) brought stronger performance. And check out that ground clearance!
Image: Mercedes-Benz Group AG

406 Series

In the late 1950s, industry analysts warned that sales of the original Unimog 411 would peak in the early 1960s, due to its small 25kW engine no longer being powerful enough for the rapidly evolving heavy mechanisation of agriculture. Analysts also correctly forecast a decline in 404 sales when initial military demand had been met.

What was needed was a more powerful variant that effectively bridged the gap between the 411 and 404. In 1963 this prompted release of the 406; the first medium-duty model which for many enthusiasts is considered the ‘classic’ Unimog in appearance, performance and versatility.

The 406 featured a new 2380mm intermediate wheelbase (2900mm for the 416), a choice of three cabs comprising single-cab cabrio, single-cab closed and dual-cab closed and more powerful engines topped by a 5.7-litre direct-injection six-cylinder diesel.

MB-trac agricultural tractor variants joined the expanding Unimog range from 1972 to 1991.
Image: Mercedes-Benz Group AG

There were also specially-designed tyres plus a stronger drivetrain to cope with the increased power, which during the 406’s long production run featured four different gearbox configurations of considerable complexity, offering up to 20 forward and eight reverse gears!

There was also a new and more powerful hydraulic system for operating an ever-expanding range of implements, while the ‘U’ internal model code initially based on engine hp was more broadly used, ranging for example from U65-U84 in the 406 to U80-U110 in the 416.

With annual improvements, the 406 series with its numerous variants (including a 421 military version) enjoyed increasing domestic and export popularity throughout the 1960s, during which the 100,000th Unimog was built. Production peaked in the 1970s, when the new 425/435 models were introduced, then gradually declined until the iconic 406 was discontinued in 1989 after 27 years of production.

425/435 series heralded a new design direction with more spacious squared-off styling.
Image: Mercedes-Benz Group AG

425 Series

In 1975 Mercedes-Benz released its first heavy-duty (9.0 tonne GVM) variant called the 425 series, with the Unimog range now offering light, medium and heavy-duty model lines. The most noticeable difference was a bold new angular cab design with a more prominent radiator grille.

The 425 had a 2810mm wheelbase and available in two models, powered by the venerable 5.7-litre OM352 inline six-cylinder diesel. A four-speed primary gearbox mated with a two-speed or dual-range auxiliary ‘box delivered a total of eight forward gears. An additional gearbox aimed at agricultural buyers added another three speeds (regular, field and crawler) resulting in a combined total of 24 forward gears!

The 425 was also equipped with switchable PTO shafts offering different rotating speeds for powering a multitude of implements, a rear three-point linkage with hydraulic height control and optional trailer brake system.

Unimog could be adapted to suit a seemingly endless list of job requirements.
Image: Mercedes-Benz Group AG

The long wheelbase 435 series, effectively the successor to the venerable 404 favoured by the German military since 1955, offered a choice of wheelbases and also available in two models based on outputs of its more powerful turbocharged inline six diesel.

The 435 proved popular with not only German defence and fire departments, but military and civil customers around the world. In 1977, the Unimog also set a new sales record with the 200,000th Unimog produced by the Gaggenau plant.

407 series cab was a mix of retro and modern styling themes. 
Image: Mercedes-Benz Group AG

407 Series

In 1985 the light-duty Unimog was revitalised as the new 407 series, identified by unique hybrid styling that combined the 425 series cab with a rounded nose reminiscent of the iconic 406 series. These were great-looking trucks.

The 407 was available in two wheelbases and powered by a robust 2.4-litre four-cylinder diesel. Even by the mid-1980s, top speed for this short-geared uncompromising off-roader was less than 80km/h!

In 1988 the medium-duty 417 was released, with a similar cab style to the 407 but with the headlights mounted in the bumper. There was a choice of four-cylinder and six-cylinder diesels with outputs up to 110hp (82kW).

408 series introduced a new off-set ramped bonnet option to maximise driver visibility.
Image: Mercedes-Benz Group AG

408 Series

The successors to the 407 and 417 arrived in 1992, in the form of the light-duty 408 and medium-duty 418. They were easily identified by their newly developed angular cabs, with steep-sloping bonnets, bumper-mounted headlights and choice of standard or high roofs. There were also two bonnet choices; standard full-width or new asymmetrical ‘viewing channel’ design with a steep ramp on the driver’s side to optimise vision.

Powered by a new five-cylinder diesel, the 408 was available in a choice of wheelbases and four models again determined by engine outputs.

The medium-duty 418 with four-cylinder diesel power was available in three models and wheelbases. However, when 418 production ceased in 1998, the slow-selling medium-duty range was discontinued.

Compact cab-over UX100 was designed for many light-duty municipal roles.
Image: Mercedes-Benz Group AG

UX100 Series

1996 brought another mild refresh of the light-duty range with the 409 series and the release of an even lighter-duty model called the UX100. It was a complete departure from the breed’s traditional design, prioritising municipal use over extreme off-road ability.

Its small size, tight turning circle, low ride height and compact cab-over-engine design were designed for easy driver entry/exit and optimum manoeuvrability in confined city streets and even on footpaths.

This made it well suited to numerous urban council roles including waste disposal and sanitation, parks and gardens, snow-ploughing etc. The fact that most people would struggle to identify the UX100 as a Unimog makes it a standout!

New high-tech cab on MY2000 Unimogs offered unmatched visibility and ambidextrous driver controls. 
Image: Mercedes-Benz Group AG

UGN405 Series

The year 2000 saw a stunning new series of beefy Unimogs launched with the power, strength and versatility required to cover heavy-duty roles in the new millennium, with robust GVM ratings from 7.5 to 16 tonnes. Underneath, they were as rugged as ever, now with four-disc ABS.

The most noticeable change was a futuristic cab design offering more interior space and outstanding driver vision. Its high-tech composite fibre construction, combining high strength with low weight, was designed by French aircraft manufacturer Dornier and manufactured by DuPont.

It also introduced the Unimog’s new VarioPilot system, which ingeniously allowed the steering column and pedal assemblies to quickly transition between LHD and RHD to best suit the driver’s job requirements.

Road Railer-equipped Unimogs have a long history of service in rail-shunting operations.
Image: Mercedes-Benz Group AG

As usual there was a variety of models and wheelbase lengths and buyers could choose between two premium diesels; a 4.2-litre four-cylinder or 6.4-litre six-cylinder with 286hp (213kW). The manual gearbox featured electric-pneumatic gear selection of eight forward gears across two speed ranges, plus six reverse speeds.

The chassis offered four sturdy chassis installation points at front, rear, side and top for mounting an unprecedented range of implements, designed to integrate with several new PTO shafts and a new VarioPower high performance hydraulic system.

Like many predecessors, it could also be adapted for rail-car shunting operations, equipped with special rollers that kept the tyres on rails. In this configuration, it was claimed the incredible Unimog could move up to 1000 tonnes of rail stock at speeds up to 25km/h in either forward or reverse!

In 2001 Daimler-Chrysler (as it was then) celebrated the 50th anniversary of Unimog production at the Gaggenau plant, during which time more than 320,000 examples were built. However, to improve production efficiencies, the following year Unimog production was moved to the company’s Wörth am Rhein plant which is the largest truck manufacturing plant in Europe.

2000s saw the introduction of the U3000-U5000 series (left) and cab-over U20 series.
Image: Mercedes-Benz Group AG

2002 also saw introduction of the first optional automatic transmission, to improve comfort and reduce driver fatigue.

The Unimog Special Vehicles product unit also revealed the new heavy-duty U3000-U5000 ‘lorry’ models, designed for extreme off-road service in large load-platform roles like forest fire control, rescue, disaster relief, long-distance exploration, mobile drilling rig operations and many more.

In 2007 came the new Unimog U20, which like the UX100 had a cab-over-engine design with very compact dimensions. However, unlike the UX100 it retained the Unimog’s extreme off-road ability and offered higher GVMs, proving ideal for numerous heavier duty roles. In 2011, Daimler-Benz celebrated the Unimog’s 60th birthday.

Latest Unimog implement carrier range was launched in 2013.
Image: Mercedes-Benz Group AG

U200-U500 Series

In 2013 came what was effectively a second (and still current) generation of the new Unimog implement carriers launched in 2000. There was new styling, new models and major enhancements across the range including new engines complying with the toughest Euro 6 emissions standard.

The entry-level U216 and U218 models were all-new, powered by four-cylinder diesels with two power outputs and three GVM ratings from 7.5 to 10 tonnes. They also had very compact dimensions, with a unique 2800mm wheelbase and tight 12.6-metre turning circle that rivalled small commercial vans, making them ideal for operating in confined spaces.

The larger U318 and U423 were also four-cylinder-powered and their shared 3000mm wheelbase was 80mm shorter than predecessors, ensuring tighter 13.7-metre turning circles.

And the new six-cylinder diesels in the premium U430 and U530 models produced an unprecedented 300hp (220kW). The optional central tyre inflation system was now easier to use, with three modes comprising road, sand and bad surface.

Hydrostatic traction drive assists greatly in smooth operation of vehicle and implements.
Image: Mercedes-Benz Group AG

Also new to Unimog was hydrostatic traction drive which allowed smooth and largely automatic operation of the vehicle, particularly at crawling speeds, along with precise and jerk-free operation of implements. When use of manual transmission was required, the operator could seamlessly switch between hydrostatic drive and manual modes while driving.

The panoramic cab, with its iconic short bonnet length and new roof-mounted wipers to optimise driver vision, brought fresh and functional styling with LED headlights incorporating DRLs mounted in the bumper. Cabin ergonomics were also enhanced to improve driver comfort, while attaching, operating and removing front-mounted implements was never safer or easier.

Latest U4000-U5000 series is popular with forest fire fighters and many other specialised clients.
Image: Mercedes-Benz Group AG 

U4000-U5000 Series

2020 brought the current iteration of the imposing U4000 and U5000 models, with cabin styling changes including a larger bonnet and more prominent grille.

With a 3.5-tonne payload rating for the U4000 and up to 7.0 tonnes for the premium long wheelbase U5000, these remarkable giant Unimogs with their signature portal axles offer up to 470mm of ground clearance (depending on tyres) and fording depths of up to 1.2 metres.

Both models are powered by a state-of-the-art 4.8 litre four-cylinder turbocharged and intercooled diesel producing 160kW and a towering 810Nm of torque. With eight forward gears and six reverse, front and rear diff-locks and a choice of semi-automatic manual or fully automatic transmissions, the legendary Unimog - after more than nine decades in production - is as capable as ever!