For those transporting heavy loads across extreme terrain, you’d be hard pressed to find a vehicle more suitable than the Mercedes-Benz Unimog. We put the larger U5023 model to the test on the arduous Gaggenhau test track on the edge of the Black Forest.
Over its 70 years, the “Universal-Motor-Gerät” (German for ‘Universal Motor Machine’; Unimog for short) has truly lived up to its name, with over 1,000 different uses under its belt. It’s been the vehicle of choice for a wide range of applications, from sweeping up half-eaten kebabs from your local high street after a heavy Saturday night to powering record-breaking expeditions across inhospitable terrains.
It’s come a long way from the dinky farmyard hand in 1946, and now the range is split into two. There is a lighter U530 model, which is used for municipal and farming work, and the heavier U5023 model (that we tested), which is used for more strenuous operations like fighting forest fires, performing rescue operations during catastrophes or maintaining power supply lines.
From the cab
The first noticeable thing when climbing into the cab is the lower floor which has made the cab feel a lot bigger and provided much more legroom. However, visibility isn’t quite as good as, in addition to the long nose, the driver’s seat has been moved further back. Compared with a conventional truck, the amount of in-cab storage is also fairly poor, although there is a large glovebox and a small overhead cabin.
To counter the visibility issue, Merc is now offering a front-end camera to give the driver an idea of what object lie directly in front of the bumper, which otherwise couldn’t be seen. There is whole host of other technology bringing it in-line with its conventional truck range, like a steering wheel-mounted gear lever, a powerful heating and air-conditioning unit and a CD radio with a Bluetooth connectivity.
Weights, measures and practicality
Mercedes-Benz hasn’t published the general payload or unladen weights of the Unimog U5023 chassis but, instead, specifies them for each individual vehicle. However, a senior technician at Mercedes-Benz has told us that the unladen weight is around 7t and, given the GVW of 12t, leaves around 5t for payload.
The turning circle of 16.3 metres is fairly tight given the 3,850mm wheelbase, while the frame length is exactly six metres long and the maximum permissible body length is 4.1 metres. Most Unimogs are used to power tools and machinery once they reach their secluded, or power deprevied, destiations which can be run-off the vehicle’s hydraulics.
The single-circuit hydraulic system supplies 240 bar working pressure, a flow volume of 60 l/min and 24 kW pump output. There are also three PTO’s (power take-offs) available as optional extras, which provide power up to 150kW.
On the road
Under the bonnet is Merc’s four-cylinder, 5.1-litre OM934 engine, which has broad power and torque curves that peak at 231hp and 900Nm respectively. This is the only Euro-6 engine that Merc offers on the Unimog, although there was previously the option of a six-cylinder engine. Our version came with the optional electronic automated transmission (EAS) with eight forward gears and six reverse gears.
Moving off, the Unimog U5023 is surprisingly quick and can reach 62mph from standstill in around 12 seconds, even with a full load on board, thanks to the low-end torque and swift and smooth gear changes from the EAS transmission. There is also a very effective two-stage engine brake
Despite rehousing the engine behind the cab and in between the two engines, the lack of cab soundproofing means quite a lot of engine and road noise perforates into the cab. However, this has worked wonders on the cornering, as the centre of gravity is now lower and more central.
Off the road
Given its huge size and weight, the Unimog is unbelievably agile and capable when the beaten track ends and the extreme and unadulterated terrain begins. We encountered a whole host of gruelling obstacles on the Gaggenhau test track, and the U5023 performed impeccably at each hurdle.
First up was the axle twist where one of the Unimog’s stand-out features comes into play. The curved frame design allows the chassis to twist and flex (up to 600mm) according to the surface conditions for maximum contact with the ground and, because the drivetrain is connected to the axles via torque tube and ball, the axles can articulate up to 30 degrees.
Next up was the incline test, which included an 80% (38.6 degrees) slope. The maximum approach angle for the Unimog U5023 is 42 degrees (46-degree departure and 32-degrees ramp over angle), so the front bumper missed by quite some distance and the 900Nm of torque meant that we could easily accelerate the 7t machine up the hill.
On the way back down, we stopped and, flicking the gear leaver forward, engaged the electronic quick reverse (EQR) which swiftly took us back up the slope without any loss of ground.
After the incline test, we activated all-wheel drive and the front and rear diff-locks and took the Unimog off-road. The Unimog has two ways of increasing traction: the differential locks can be engaged to prevent wheel spin; and the central tyre inflation system adjusts the surface contact of the tyres to the type of ground.
There was nothing on the course that proved challenging for the Unimog, as the portal axles gives an increased ground clearance of 410mm, which was a lot higher than any of the rock on our route, and the 1.2 metres (800 on standard variant) wading depth was a lot higher than the river that we crossed.
Pricing and availability
The Unimog U5023 can be ordered through the Merc’s 110-strong Commercial Vehicle dealer network, although very few stock demonstrator models. Mercedes-Benz doesn’t publish the list price, but an entry-level chassis cab, without any body, is expected to set you back around £100,000.
With the combined force of the two Unimogs and the even larger Zetros, Mercedes-Benz dominates the heavy-duty 4×4 sector. At the helm of the steering wheel, no mountain is too high and you can easily imagine yourself trekking across the glaciers of Patagonia or navigating an overgrown Himalayan mountain trail and, for that quality alone, we’re always going to give it five stars!
However, there is very little practical use for the U5023 in 21st century Western Europe. Our roads are well developed and for most off-piste applications, a pickup and generator to run the tools would be suffice.