The new high-mobility Unimog U 3000, U 4000 and U 5000 model range has been developed for difficult all-terrain operations far from the nearest roads or tracks. It went into production at the end of August 2002 at the new Unimog facility within the Wörth truck plant of DaimlerChrysler AG, thus succeeding the heavy-duty Unimog U 1550 L, U 2150 L and U 2450 L range of all-terrain chassis which was produced in Gaggenau until the middle of the year 2002.

With its superior off-road capabilities, the Unimog U 3000 – U 5000 model range is the natural choice for extreme-terrain operation and international security duties. The high-mobility Unimog U 3000 - U 5000 range combines the traditional Unimog virtues such as soundness, robustness, long life, reliability and the almost legendary four-wheel-drive concept with state-of-the-art engine and transmission technology and excellent ergonomics. More than ever before, outstanding operational reliability results in superior overall cost-effectiveness, with reduced maintenance costs and a high resale value.

The principal applications of the Unimog U 3000 – U 5000 model range will be in fire-fighting - particularly in forested areas - in disaster aid, as a chassis for expedition vehicles, as a transport vehicle and for carrying out service and maintenance work at out-of-the-way locations. It therefore ideally complements the Unimog U 300 to U 500 all-terrain implement carrier range first unveiled in spring 2000, which is used mainly by public services and municipal contractors, in the construction and energy industries and in intra-plant transport.

Highly elastic, torsionally flexible frame

The Unimog owes its unrivalled off-road capability amongst other things to its special frame design, and the Unimog U 3000, U 4000 and U 5000 models are no exception. High torsional flexibility is essential if a wheeled vehicle is to navigate terrain which would otherwise be out of bounds to land-based means of transport except perhaps tracked vehicles.

The ladder frame of the high-mobility Unimog U 3000 - U 5000 models consists of two U-shaped side members which are welded to tubular cross members. The various elements of the flexible ladder frame are designed both for adequate stiffness in fast on-road driving and also for high torsional flexibility in off-road operation.

Choice of two wheelbases

All models in the high-mobility Unimog range are available in two wheelbase versions: 3250 mm and 3850 mm. The short wheelbase is particularly suitable for applications where compact design and manoeuvrability are paramount, while the long-wheelbase versions are ideal for use with larger bodies or combinations of bodies.

Three-point mounting for components and body

Three-point mounting of the engine and transmission plays an important part in ensuring the high torsional flexibility of the high-mobility Unimog. The cab and bodies are likewise mounted at three points, while for longer bodies a twin three-point mounting system is used. The three-point mounting concept is clearly visible whenever the vehicle is negotiating large, diagonally positioned obstacles with height differences of up to 500 mm. In this event the body or mounted equipment tilts at a different angle from the cab. The resulting large relative movements produce no mechanical stressing which could be harmful to the vehicle or body.

Suspension with torque tubes and coil springs for maximum articulation

A further crucial factor in the unbeatable off-road mobility of the U 3000 – U 5000 range is the design of the suspension. Portal axles front and rear with spur gear hub reduction give the high ground clearance which is essential for extreme-terrain operation. What’s more, hub reduction means that the torque is developed exactly where it is needed, namely at the wheel, thus reducing wear on the powertrain.

The axle location by means of torque tubes, control arms and coil springs results in long spring travel and axle articulation of up to 30 degrees. A further advantage of this design on the high-mobility Unimog is that drive forces are transmitted centrally to the frame, via the transmission housing. Also, since the drive shafts are mounted inside the torque tubes, they are extremely well protected against damage during operation in punishing conditions. For off-road operation, this is a definite advantage over exposed drive shafts.

Even the basic version of the Unimog U 3000 - U 5000 offers a fording depth of 800 mm for negotiating water and mud. An optional fording system gives a maximum fording depth of 1200 mm and provides reliable protection against penetration by water, dirt or very fine sand.

The Unimog U 3000 to U 5000 model range is equipped with disc brakes on all wheels. A new feature of the hydraulically operated, pneumatically assisted system is standard-fitted four-channel ABS, which is disengageable for off-road operation and which regulates each wheel individually. For wearfree auxiliary braking, the high-mobility Unimog is equipped with a two-stage engine brake. The first stage is a constantly open throttle valve brake and the second an exhaust valve brake.

No-compromise four-wheel-drive engineering

A basic feature of the high-mobility Unimog family needless to say is traction-enhancing, no-compromise four-wheel-drive technology. This comprises front-wheel drive which is pneumatically engageable while on the move plus 100 % full-locking differentials front and rear.

Both of these traction-enhancing functions are activated simply by turning a handily placed dashboard control to the right of the steering wheel. Stage one engages four-wheel drive. Stage two provides 100 % locking of the complete powertrain. This stage too is selectable pneumatically while on the move.

Standard-fitted electronic-pneumatic Telligent gearshift

The eight-speed Unimog transmission UG 100-8 is supplied as standard with the electronic-pneumatic Telligent gearshift. Using the compact shift lever unit next to his seat, the driver can directly engage or pre-select the eight gears as required. Large figures in the central multifunction display situated between the tachograph and the rev counter indicate the currently engaged and preselected gears. Pre-selected gears are engaged using the clutch pedal.

Gear changes require no physical effort on the part of the driver. The work is performed by pneumatic servos on the Unimog transmission, under the supervision of a transmission computer linked to the engine management. This rules out any risk of incorrect gearshifts. When the driver operates the EPS shift lever knob, the transmission will suggest what it calculates to be the most suitable gear in any particular driving situation. The driver can accept this recommendation by depressing the clutch, or he can correct it in accordance with his assessment of the situation by a touch of the shift button. The basic principle is that the driver can change directly into, or can preselect, the next gear up or down by operating the shift button (situated on the front of the shift lever), while a recommendation of the most suitable gear is requested by operating the actual shift lever knob.

Easy, convenient and quick forward/reverse shifting with „Electronic Quick Reverse“ (EQR) reversing gear

But the driver convenience of the high-mobility Unimog series does not stop at the gearshift. The development engineers have also equipped the U 3000 – U 5000 models as standard with an EQR („Electronic Quick Reverse“) quick reversing system.

The technical basis for this system is the synchromesh forward/reverse gear set on the transmission input shaft. EQR is activated by pressing a switch behind the EPS shift lever unit, whereupon the EPS button acquires a new function. Now the driver can use this button to pre-select a change of direction. Shortly before stopping, he can then switch immediately from forward to reverse drive, or vice versa, simply by depressing the clutch. This makes it possible to change direction quickly in confined spaces, or to „rock“ the vehicle out of a mudhole with minimum stress on clutch and transmission. Thus EQR provides significantly enhanced driver convenience.

16 heavy-duty gears

The standard version of the Unimog U 3000 - U 5000 chassis already offers an eight-speed main transmission suitable for most applications, with a wide gear spread and low-ratio first gear. For increased traction in extreme terrain, or for slow manoeuvring over difficult obstacles, a working/off-road gear range is available which provides a further eight heavy-duty gears spanning a speed range from 1 km/h to 15 km/h. This means that however extreme the terrain, the driver can drive with the clutch fully engaged and always remain on top of the situation. Thus there is no need to slip the clutch, which in off-road terrain can be highly dangerous for both driver and vehicle.

Strong power and torque from Euro 3 turbodiesel engines

The high-mobility Unimog U 3000, U 4000 and U 5000 model range is powered by state-of-the-art Euro 3 diesel engines in different output ratings. The U 3000/ U 4000 models, with a perm. gross vehicle weight of 7.5 t to 9.5 t, are fitted with the 900-series intercooled four-cylinder turbo engine which has proved its worth for many years in Mercedes-Benz trucks and buses. The OM 904 LA has a displacement of 4.25 litres, a rated output of 110 kW (150 hp) at 2200 rpm and delivers its peak torque of 580 Nm between 1200 rpm and 1600 rpm. For the 9.5-t model (available in a 10.0-t version for fire-fighting applications), the OM 904 LA has a rated output of 130 kW (177 hp) at 2200 rpm. The peak torque of 675 Nm is again delivered at between 1200 rpm and 1600 rpm.

The top-of-the-line model in the high-mobility, heavy-duty Unimog range is the U 5000. Its permissible gross weight of 12.5 t can be increased, for fire-fighting applications, to 14.1 t. Its engine, which is matched to the higher vehicle weight, is the OM 924 LA, a newly developed version of the above-mentioned OM 904 LA turbodiesel. The Unimog is the first vehicle to be fitted with this engine. The displacement is increased to 4.8 litres which, along with further modifications, for example to the electronic injection system, gives a rated output of 160 kW (218 hp) at 2200 rpm and maximum torque of 810 Nm between 1200 and 1600 rpm.

Highlights of the Unimog’s 900-series engines include the powerful low-end and middle-range torque which is all-important for heavy-duty off-road operation, along with application-matched high rated output for fast long-disance on-road driving, for example in international disaster aid work.

The state-of-the-art design of the 900-series engines translates into high mileage capability, long lifecycles and low running costs, not least due to improved fuel economy. The engines used have a Euro 3 emissions rating and have the potential to meet even more rigorous limits in the future.

Completely redesigned driver’s station, with ergonomically arranged controls

The high-mobility U 3000 – U 5000 models feature a new-look driver’s station housed in a tilting all-steel cab with torsion-free mounting. The cabs come in two- or three-seater solo versions or as crewcabs with up to six seats and can be easily identified from the outside by their new front-end design.

The inside meanwhile has been radically revised. In the driver’s station, all the information required for safe operation of the vehicle is presented in a practically designed instrument cluster whose state-of-the-art backlighting makes it easy to read at night or when visibility is otherwise impaired. The instruments include a rev counter, speedometer, coolant temperature display, fuel gauge and brake reservoir pressure display for brake circuits one and two. There is also a multifunction display between the speedometer and rev counter which amongst other things shows the currently engaged gear and the pre-selected gear, if any.

To the right and left of the steering column are combination stalks of the type which have proved particularly successful on Mercedes-Benz trucks. The stalk on the right is used to control the standard-fitted two-stage engine brake, the cruise control and the speed limiter. The stalk on the left operates the direction indicator, the three-speed screenwiper, the horn and the high beam.

Also new are the switches to the left of the instrument cluster and the new, convenient position of the parking brake control, to the right of the steering wheel. On the far right hand side of the instrument panel, in front of the front passenger seat, is the electrical/electronics compartment, which is situated in a dirt- and moisture-protected location. The area above the windscreen houses equipment like the EC tachograph and the radio. A variety of generous stowage spaces in the Unimog cab provide plenty of room for keeping objects safely stored even in extreme off-road situations. Overall, the U 3000 – U 5000 Unimog model range provides some 80 % more stowage space than the vehicles and chassis of the previous heavy-duty series.

The new Driver Information System (FIS)

Situated between the permanent displays is a central alphanumeric display which provides variable information, in both symbol and text form. The new „Driver Information System“ (FIS) - an on-board computer mounted above the shift gate display - shows additional information as appropriate, for example when the differential locks or four-wheel drive are engaged, or when the cruise control, speed -limiter etc. are in operation. The basic menu also shows external temperature. Another menu allows the driver to request further information and to adjust the settings.

The Driver Information System (FIS) is operated by means of buttons to the left and right of the instrument cluster. This new system supplies the operator with all relevant data about the current operating status of the vehicle.