Mercedes-Benz Unimog U4000 First Drive
The Actual Ultimate Driving Machine: Are Life-Changing Experiences Supposed to be This Much Fun?
"In this gear, the maximum speed is 80 meters per hour," Siegfried Burow tells me. I can hear the U1450's diesel engine making noise, but our forward progress is imperceptible. Again, we're moving at 4 feet per minute. I should explain that this particular Unimog has been outfitted with a set of ultra-low gears, bringing its total up to 32 speeds -- eight forward, eight low, eight ultra-low, and eight reverse. Why eight reverse? "Well, let's say you have to back up a train," Karlheinz Guttman explains with a straight face. "You might want to start slow and then speed things up." It's true, you might.
The real answer to the question "Why?" is that since it was developed in 1946, the Unimog (short for Universal Motor Geraet, or Universal Motorized Machine) has always been about maximum functionality. Intended to be a replacement for a conventional tractor, Unimogs never really set the agricultural world on fire. Farmers, it seems, are just fine with their tractors. Militaries the world over, however, absolutely love them some Unimog because of its ability to do damn near everything. Like towing trains, moving at speeds as slow as 4 feet per minute or -- most important -- being able to get to the same places as a tank.
Guttman and Burow are curators of the Unimog Museum in Gaggenau, Germany, halfway between Stuttgart and Strasbourg, France, home to the original Unimog factory. While small, the museum does house a great collection of Unimogs, including Prototype #6, the earliest surviving Unimog there is. (Fun fact: The original track was 127 cm wide because that's the same as two rows of potatoes.) The collection also contains several early 400 series 'Mogs, including a bafflingly cute Swiss fire truck with a 40cm wheelbase extension, because a Swiss law mandated that all fire vehicles must be able to seat eight people.
"I ran up a 40-percent incline, then jammed down the backside of the hill into 2 feet of frozen water"
What's so incredible about the prototype is that all the key aspects that define Unimogs to this day are present in the original. First are the portal axles. Instead of the ends of the axles entering the center of the wheel, the shafts enter the top of the wheels and are then geared down. This effectively doubles the truck's ground clearance. The next key trait is the hyper-articulating suspension. Each solid axle is able to rotate up to 30 degrees in either direction. (The torque tubes fit into the transmission via a ball joint.) Moreover, the engine and transmission are attached to the frame only in three places, on rubberized mounts. When called for, this setup provides extra twisting ability.
The final piece of the Unimog puzzle are the unique transmissions. Even the earliest versions provided for several forward speeds (six in 1946!) and multiple reverse gears. Prototype #6 had two, whereas modern 'Mogs have up to eight. Reverse on a Unimog works similarly to low gears (transfer case) on traditional 4x4s. There's a second lever (on manual trucks) for selecting forward or reverse. All you need do is clutch in and throw the lever, and suddenly you've gone from fifth gear to fifth in reverse. They also have the from-the-factory ability to accept geared power takeoff units to run more than 3500 implements, from snow blowers to seed spreaders to grass trimmers.
Behind the museum is a small yet severe Unimog parcourse with an idling 2012 U4000 doka, or double cab. Burow was in the driver's seat and eager to give me a run around the course. Guttman gave me a copy of "Faszination Unimog Museum," a book about the museum's history that happens to contain a photo of Burow building the parcourse. Who better to take me around?
Two-dimensional images don't do justice to the severity of the course and its obstacles. From my perspective, the U4000 scaled a wall, climbed a staircase, drove on its door, and rode over boulders. Then, Burow ran the entire thing backwards. The mighty 'Mog didn't even sweat, let alone even kind of get stuck. I was having so much fun, I invited the photo and video crew inside to have a couple laps. As far as I know, they're still smiling.
After the museum, we went to an abandoned rock quarry near Rastatt that's been converted into a Unimog playground. "Wonderland" is more apt. There were 45-percent grades, 4-foot-deep water obstacles, rocks, mud pits, tortuous trails, and specially designed piles of concrete to show off the fact the driver-side front wheel can be 1 meter off the ground. At the same time, the passenger-side rear wheel can also be 1 meter up. All too often, trucks and SUVs are described as having the ability to "go anywhere." But I can't think of another production vehicle I've ever been in that could do one-quarter of what the U4000 did.
Finally it was my time to drive. The biggest difference between driving a Unimog and a normal truck is the transmission. While there is a full automatic mode, for severe obstacles you naturally want the ability to select your own gears. (You don't really need first through third gears for normal driving. The U4000 can happily take off from a stop in fourth gear.) If you do decide to slip the clutch, there's a vestigial clutch pedal that can be released. The U4000 I drove had eight forward gears, six reverse, plus an additional eight in each direction when you're in low. You press forward on the gear lever to go up, pull back to go down, and there's another button below it to engage forward or reverse. You literally just flick it. I'd say it's about 2 minutes of learning and then you're good to go, well, anywhere.
I set off and headed for a steep, muddy incline. The Unimog bounded up the slope like it wasn't there. Then I realized that I was still in RWD. The thing about Unimogs is -- and this goes all the way back to the prototypes -- once you engage AWD, the center differential is locked. (Technically, there is no center diff, but once the front driveshaft is engaged, the ratio is locked and torque is split 50/50.) Like all Unimogs, the front and rear differentials can be locked. On modern 'Mogs you can choose which axle to lock via pneumatics. And you can engage the low gears in RWD. I never did anything severe enough to warrant using the lockers, but I found a few places in the quarry where AWD was required.
The highlight for me was running up a rutted, muddy 40-percent incline and then immediately jamming down the backside of the hill into 2 feet of frozen water. I crashed through a sheet of ice, and it's something I'll never forget. While I was behind the wheel of the Unimog for only half an hour, I laughed the entire time. Supercars are far less fun. Color me massively and completely impressed.