Two Unimogs Still Ready to Work After 40 Years of Service

Kamil Kaluski
by Kamil Kaluski
The UNIversal-MOtor-Gerät, better known as the Unimog, is a portal-axle-equipped toy for the super-wealthy — or that’s what most people think, thanks to it often pictured as a luxury camper van in the depths of the wild. But all over the world, Unimogs spend their lives doing the kind of work they were designed to do in construction, railroad, utilities, fire departments, agriculture, and non-combat military. Overland expeditions, ironically, were the one function for which they were not originally conceived.The truth is that anyone can buy a used Unimog for a reasonable amount of money. In fact, my friend and 24 Hours of Lemons teammate Mike owns two. That’s right; my teammate owns not one, but two Unimogs! That blew my mind, because, seriously, how often do you even see a Unimog anywhere, never mind know a man who owns two?
The Unimog design can be thought of more as a tractor than a pickup truck. Over the years, Unimogs were available in many wheelbases and several cab and bed configurations. There are equipment attachment points in the front and in the back, hydraulic connections for control of those attachments, and power takeoff points, commonly known as PTOs. Depending on the use and application, many different attachments can be added, such as lifts, plows, snow blowers, cranes, brush mowers, and augers. When equipped with rail axles, the Unimog can improvise as a locomotive due to its low gearing and drawbar towing capacity.All Unimogs have portal axles, which raise the axle center above the wheel center, resulting in a very high ground clearance and specific look. Unlike most 4WD vehicles, the transfer case is part of the main transmission, not a separate component. The power is permanently sent to all four wheels and both axles are equipped with air-powered axle differential locks. Short overhangs maximize approach and departure angles. Sealed powertrains and drivelines, snorkels, and exhaust stacks allow Unimogs to ford very deep waters.The suspension system is also unlike any other vehicle. Until the UGN-series, which was released around 2000, all Unimogs utilized torque tubes. Torque tubes enclose the front and rear driveshafts and serve as part of the suspension. These torque tubes locate the axle fore and aft, and a panhard bar locates the axles from side to side. Coil springs are fitted to all four corners and no other links are used to position the axles. This system allows for maximum axle articulation, reduces unwanted axle movement, and protects the driveshafts.
Mike’s two Unimogs were both produced in 1976. The yellow one is a J.I. Case MB4/94, or a rebadged Mercedes Unimog 406, known by its sales designation as U900. It has a naturally aspirated six-cylinder 5.7-liter OM352 engine, and was originally purchased from J.I. Case by the Sacramento Municipal Utility District (SMUD!) with a front-end loader and a backhoe. It’s unknown if the backhoe had issues, but the mount for it at some point was partly torched off and a Mercedes-style three-point hitch was installed. The entire back deck that sits on the frame is a J.I. Case unit, and the backhoe and other attachments, including their own three-point hitches, sat on hooks that interfaced with the Mercedes-style three-point hitch.The red Unimog is a Mercedes U1500 with a turbocharged six-cylinder 5.7-liter OM352 diesel engine. After falling in love with the U900, Mike just had to have the burlier-looking U1500 when he found it. After gaining his wife’s blessing, Mike made two cross-country trips and arranged shipping to bring the U1500 home. He bought it from an importer, who brought it to the U.S. from the Middle East. It’s equipped with a flatbed that tilts in all three directions, and a commercial domestic snow plow.For the U900, Mike has a front loader, 5-foot rototiller, 7-foot flail mower, and front backfill blade. Everything except the loader would work behind the U1500 without too much effort. The only differences are adapters for the PTO shaft size and three-point hitch.
The U900 has a 20-speed transmission, with a 6-speed main shifter. The U1500 has a 24-speed transmission, with an 8-speed main. Both vehicles have separate forward/reverse levers, which allow the same speeds going in reverse, a feature that’s handy on a railroad. Both also have selectable intermediate, crawler, and super-crawler gears. When in crawler and super-crawler, the top two gears are locked out.The U900 is running Continental 14.5R20 E6s tires. The U1500 is running on oversized Michelin 16R20 XZLs, which may have come from a HEMTT. Each XZL tire is rated for 14,500 pounds, and the U1500 empty weighs about 13,000 pounds, so they are a slight overkill. Each of the XZL tires weighs about 380 pounds and each wheel weighs about 40 pounds, so each mounted wheel and tire is over 400 pounds.
Mike is an off-road enthusiast, but he does most of wheeling in his TJ Wrangler. His Unimogs still see a lot of use as he plows the long dead-end street he lives on and uses them for chores around his large property. His ‘Mogs are far from pretty, unlike the restored ones seen for sale at boutique dealers, but fully mechanically functional, which is what’s important to Mike. Despite having an impressive four-car garage, the Unimogs have to live outside due to clearance issues.The red U1500 is rather imposing, mostly due to its height. The cab is about five feet off the ground and the bottom of the seat cushion is a good six feet up. Being tall has its benefits here, as the climb into the cab will make you feel as if you are a toddler climbing into a top bunk bed. The U900 is completely different, however, as it is much lower and front fenders take up a lot of leg room. Where the engine is in front of the cab on the U1500, the engine in the U900 protrudes into the cab due to its smaller size, resulting in decent size dog house inside. By comparison, the U900 cab feels very cramped.
All old vehicles have issues and these complex Unimogs certainly do too.The U900 had a leaking transmission seal on the front axle output. Gear lube would flow past the seal, down the torque tube, into the differential, and finally slug out at the double-cardan joint at the knuckle, behind the portal box. To replace this seal, the entire front axle has to be disconnected and pulled, as the drive-shaft is inside the torque tube. Mike says that this was an “interesting job” that required special tools and lots of patience to master the German art of stuffing ten pounds of mechanical crap into a five pound space. The U900 also had miscellaneous electrical issues caused mostly by corrosion and the old style GBC fuses (the ceramic ones with a piece of metal running down the outside). He also had to replace several hydraulic lines. In order to keep costs reasonable and cut shipping time, the housings were custom-made by a local shop.Rust is the biggest issue on the U1500. There was one incorrectly assembled locker motor, an air piston on the outside that engages the internal bits, on the front axle. Mike also had to rebuild the three-point hitch lift cylinders. Brakes had to be overhauled and required the rebuild of all four front calipers (two calipers per rotor, 4 pistons per caliper), a rebuild of the master cylinder, and replace the air cylinder at the master cylinder. Soon, Mike will be replacing the clutch, which sounds like a fun way to kill those long boring summer months.
Part availability is not as big of a problem as it may seem. Common parts are usually available from one of the three primary parts dealers in the U.S., as they have bought up surpluses of NOS part lots as they’ve become available over the years. When those dealers don’t have a part, they can usually get it directly from Mercedes-Benz in Germany. If the part is not available there, someone has generally figured out a work-around or retrofit for a later style. For example, the U1500 used to have a cable running from the brake pedal to an air valve on the frame rail. The frame rail valve was no longer available and the cable only complicated matters. A company in the UK developed a kit that replaced the brake pedal assembly, cable, and brake valve with a new pedal assembly and firewall-mounted valve.Being essentially a tractor, Unimogs were not designed for speed. The U900 with loader and counterweight will top out at 45 mph, be it going down or uphill. Keeping that speed requires a lot of shifting, however, due to the engine’s narrow powerband. The U1500 can do steady 50-55 mph and may top around 60 mph. The more flexible turbo engine results in less dramatic hill climbs.
Unimogs are some of the most capable vehicles in the world. They were designed for a variety of specific tasks, when properly equipped and in the hands of properly trained people. While some rich or famous folks (Arnold had one) attempt to drive them daily when they’ve outgrown their Geländewagens, or vacation in them, they are best used as intended. Like any other specialty machine, they also require more service than a typical Camry. For most people, owning one makes as much sense as owning an Ariel Atom, but we should all appreciate these awesome machines.Kamil Kaluski is the east coast editor for Hooniverse.com. His ramblings on eastern European cars, $500 racers, and other miscellaneous car stuff can be found there.
Kamil Kaluski
Kamil Kaluski

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  • Scout_Number_4 Scout_Number_4 on May 21, 2016

    *How can someone *not* love a Unimog?* Completely agree with this. There's one for sale here in Portland at BHPH lot on 82nd Ave for at least 2-3 months. I keep thinking I should go ask for a test drive before it finally sells. http://www.atlasmotors.com/en_us/unitdetail.asp?used-1969-mercedes-unimog-portland-or-=573460

  • Ermel Ermel on Jun 11, 2016

    Unimogs are tools. They are huge outside, cramped inside, noisy, hot in summer, cold in winter, and have a very harsh suspension. They are really rather slow in both accelleration and top speed, and guzzle Diesel like it was beer. As a return, they get you wherever you need to go, period. And actually going there, or otherwise using them to anywhere near their capabilities, is great fun. Driving them on the road (and anything where an SUV can make it counts as "road" in this sense), not so much. In other words, they might be the upgrade path for the guys that go offroading in their Wranglers and Defenders, but not for the type who brag about their Rams and F-150.

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