It’s all fun & games until someone loses a drive train…

It’s all fun & games until someone loses a drive train….

Don’t worry. It wasn’t our’s. But you can bet your ass that we work hard to stay on top of all the regular & preventive maintenance for this beast.

There definitely seems to be an uptick in the number of military trucks reincarnated as monster RVs out there. While we may not have started the trend, we think it’s pretty safe to say that as long as keeps auctioning off perfectly good LMTVs and MTVs for pennies on the dollar, there are going to be a solid number of people looking for advice on what to do with one once you get it home from the auction.

Have no fear — you got this. Here, we outline our first 8 months of repair & maintenance with our M1083. (Disclaimer: This is just our experience. Don’t take it as law and please don’t cry to us when your experience isn’t exactly the same. Use common sense. Find a good mechanic if you’re not one & ask them questions. Do your due diligence about the truck you have in mind. You know the drill…)

Let’s start at the beginning. You should know a few basic things about the LMTV series of vehicles before you consider buying one at auction no matter how cheaply you can find one for:

  • If you don’t already know that the LMTV series of trucks is cab-over and that the cab is raised to access your engine, do not pass go. Do some Google searches and familiarize yourself with this chassis before you pull the trigger. And if you can get your hands on one of the BAE, Stewart & Stevenson, or Oshkosh Truck LMTV operating manuals before you make your purchase, it will unearth a lot of answers you may be pondering as you consider if this platform is right for you.
  • They generally operate on a CAT 3126 engine with an Allison transmission. Good news: You can get them serviced just about anywhere in the world. In the US, that means many places right off the highway near truck stops. Bonus? Many truck service shops have local government contracts and, therefore, often have folks on staff who know these trucks inside & out. Don’t tune out when you go for service — Listen & learn.
  • When you buy one, take it to a good CAT shop for a complete engine and transmission service. Have the brakes checked, hydraulic lines replaced and air lines checked and replaced as necessary. Replace the starting batteries, and get new tires if necessary, as tires wear by miles, not just by age.  Think preventatively. What may cost you a few hundred dollars today will save you a lot tomorrow. Costs will vary by age of vehicle, its usage history, and location where the service is done. But it will be money well-spent.
  • Do you need a special license to drive one? Nope. Just register it as an RV. (Some states have restrictions on this; check with your state). The caveat? You should familiarize yourself with using air brakes and get acquainted with the systems before you let her rip. If you’re a standard RV’er and move into one of these without learning how to drive like a trucker, you might set yourself up for some misery on the road.

In August 2016 when we purchased our M1083, it had 11,754 miles on it. Our truck was purchased and serviced by GXV, so we won’t go into the nitty gritty details of all the initial work in this post, instead elaborating more on our maintenance and repair work since taking ownership.

As of this post, it has roughly 29,000 on it, so we’ve had just over 17,000 miles of wear and tear. Due to work, most of it has been on-highway driving, but we do occasionally drive heavily rutted, steep or slippery forest service roads and over things that most trucks can’t. Your maintenance schedule will be dictated, at least in part, by how much abuse your engine gets.

Meet Trucky McTruckface, a project by our friends over at @overlandadventuretruck.

Let’s start with some basic maintenance:

  • Oil Changes: Every 5,000-7,500 miles (CAT says every 7,500-10,000 but we figure it’s cheap insurance to do a little more regularly). It takes roughly 6 GALLONS of oil (you heard that right) at about $18/gallon, so you can save yourself some money by doing them yourself. (And it’s kind of fun since the truck is taller than a regular vehicle). These things guzzle oil, so always keep some handy for top-offs on long trips. If you take it to a shop, expect around $250-450 depending on the city and whether or not you’re supplying your own filters.
  • Oil Filters (1) & Fuel Filters (2): Change regularly when you change oil. The primary oil and fuel filters together cost about $36. Every 2-3 oil changes we change the secondary fuel/water separator (~$15); more frequently in winter, less in summer.
  • Air Filter: Change 1-2 times/year (or every 15,000 miles), depending on driving, to the tune of about $75.
  • Generator Oil Changes: Change oil every 50-100 hours (again, it’s cheap insurance to just do it a little more frequently even though the manual says every 100 hours). Our’s takes about 1⅓ quarts of oil and uses a metal filter that gets cleaned instead of replaced.
  • Tire Changes: The tires are good for roughly 40k miles, and we budget about $6,000 to replace them when the time comes. It’s not a surprise expense, so just budget monthly over the course of a few years and voila.
  • Other Parts: It’s not a Mercedes, so most everything you need for the truck can be obtained at any standard auto parts store (air filters, oil for generator and engine, etc).  We rely daily on parts like our 50′ air hose so we can change pressure and manage small air leaks from the on-board air compressor.

On to repairs. Keep in mind that, in many cases, these trucks are more than a decade old and haven’t been used regularly (our’s is a 2001). They’re bound to have a few malfunctions until all the kinks are worked out, and we have budgeted roughly $5,000-10,000 for our first year. (We’re currently on the low side of that estimate). We’re already noticing better fuel economy (now at 8.1 mpg consistently), smoother ride, and a generally happier truck now that it’s seeing regular usage.

  • DRIVE SHAFTS – We would be remiss if we didn’t talk about these first given the title of this post… Luckily, Martin is cautious and smart about regular maintenance, otherwise it could have been us losing a drive shaft. No fun. There was a little play in the front one, and the second and third were completely dry. It turned out that when we bought our truck, the CAT dealer in Missouri replaced one U-joint and certified that the rest were fine, but they failed to check their lubrication. When we discovered this, in the abundance of caution, we replaced them all. Drive Shafts 101: These guys connect axles to transmission. If one breaks on the back end of a 6×6 truck like our’s, it can flop around and damage the hydraulic or air lines. If it breaks on the front or middle, it can spike into the ground and destroy the transfer case & transmission, ruining your day (and quite possibly your life).
  • INJECTORS – The diesel injector in the second cylinder malfunctioned a few months in. We noticed a sudden loss of power and, fortunately, were within just a few miles of a CAT shop outside of Seattle. There’s really no rhyme or reason to injectors going to bad; it can happen in the first mile or after a million miles.
  • BRAKES – Our air can went bad on the passenger side middle axle, causing the brake to drag and not release. These cans control the inflow/outflow of air needed to operate the air brakes, and these just apparently wore out over time. This was an expensive fix because the first few shops we visited didn’t have the parts to fix it. We had to have it capped off at a shop near Portland just to get us by, and then found the master brake repair specialists at Precision Truck & Trailer in Salt Lake City. Guys there actually engineered the brake systems for these trucks, so not only were they able to fix the problem, they taught Martin a LOT.
  • FUEL TRANSFER PUMP – Our Jabsco impeller-driven pump went bad and was replaced with a gear-driven pump to move fuel from other tanks in to the working (day) tank. As we’ve found with so many systems on the truck, simpler systems almost ALWAYS work better.
  • TRANSMISSION LEAK – Initially, we found that our transmission fluid was constantly low. This issue fixed itself with regular driving, however. The truck probably just sat too long and  the output seal on the transfer case was weeping. The more we drove, the more the transmission fluid lubed up the seals and gaskets, making them work again.
  • AIR LEAKS – Since trucks with air brakes and air systems have dozens of air connections, they do generally have some sort of leak. It’s normal. We’ve probably fixed half a dozen by crawling underneath the truck with a spray bottle of detergent and seeing where the lines bubble (just like fixing a bike tire). Find them, tighten them. Rinse, repeat.

Here’s a breakdown of what we’ve spent so far. The totals include all the parts, oil changes, filters, services, repairs…basically every little thing we needed to ensure a smoothly operating truck (other than fuel) for 16,000 miles over 8 months:

    • Aug – $43 (parts for new truck)
    • Sep – $346 (parts)
    • Oct – $257 (oil change)
    • Nov – $1895 (injector repair, parts, miscellaneous)
    • Dec – $1360 (brake repair, oil change)
    • Jan – $1522 (drive shaft replacement, parts, miscellaneous)
    • Feb – $35 (oil)
    • Mar – $573 (oil change service, air filter and tire repair & rotation

      $6,031 total ($754/month)

Changing out the tires on these isn’t so bad…You just need the right tools for the job.
The crew at West Valley Tire in SLC did it in no time.

Depending on your budget, you may be either shocked at that sum or think it’s no big deal. We think of it this way: We aren’t spending any money on yard maintenance, car maintenance, utilities, property taxes or other expenses in owning a home. In perspective, even considering some of the minor things we’ve had to repair/replace, it’s still well within our expectations for driving a tiny-home-on-wheels full-time. Overall, it’s been an ideal platform for an off-road RV. If you know a few of these things ahead of time and are willing to do your homework, you can save yourself some major headaches when you choose to go down the LMTV road. Good luck!







  1. If my pumpkin is junk and I want to change to front wheel drive. What is simplest way?

  2. Martin says the cab lift hydraulic fluid can be topped off through the fill plug, usually a hex key, located near the hand pump. Good luck!!

  3. Just purchased an LMTV 2.5 ton and the cab latch piston is leaking… Where do you fill the fluid up? I want to fill the fluid, then raise the cab (yes it will be leaking) then remove latch assembly replacing the o ring and general cleaning. Can you help please?


  4. This CTIS is notorious for failure too. 6 flat tires is a bad day.

    I would also add that on these trucks the fan clutch needs to be checked for wear. It is a very special clutch that has an air line attached to it from the air compressor system. They have a replaceable clutch liner. On some clutches the screws will back out and allow the clutch to go flying ( I found this out). There is risk for overheating if the clutch is not operating correctly. People have also said that the fans weaken over time and will take the radiator out.

    If it is plastic and it is the original component on these trucks, it should be checked routinely.

  5. The CTIS defaults to too low an air pressure for what we use on highway driving to maximize our fuel economy. Therefore, we find it faster and easier to just fill it with the hose to our desired pressure before each trip.

  6. Wait, I thought these had central tire inflation. What are you using that 50′ hose for?

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