Mil-Spec M1-R First Drive Review | The ultimate Hummer H1 gets better

In 2018, we got our first introduction to Mil-Spec, a company that sought to do to Hummer H1s what other resto-mod companies like Singer and Icon have done to other classic cars. Its initial run of hopped-up Hummers showed quite a bit of promise with an array of mechanical upgrades, including a particularly potent and entertaining diesel engine, plus major improvements to interior livability and luxury. As good as the initial trucks were, Mil-Spec wanted to do even better. It focused on details such as better materials and ergonomics for what it’s calling the second-generation of restored H1s. And all those upgrades are on display in the M1-R, which takes the second-gen M1 and adds some pretty extreme customer-requested modifications.

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What’s that? Oh nothing, just a Mil-Spec M1-R rolling on by ##autoblog ##hummer ##m1r ##custom ##fyp

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As with all Mil-Spec Hummers, the M1-R received a comprehensive restoration, taking the body and frame down to bare metal. It was recoated in a durable bedliner-style material made with bits of Kevlar. This particular one was given a tint to make it look like one of the factory H1 colors, Competition Yellow. Steel off-road bumpers, a front brush guard, rear tubular tire rack, fender flares and door panels finished in plain black add contrast and help give it a more rough-and-tumble look. The simple and rugged 20-inch Black Rhino wheels look right at home on the truck, too, especially wrapped in the 38-inch off-road tries.

Most of the improvements in the second-gen M1 are found within the cabin. As before, every upholstered surface is made of leather, in this case with diamond stitching that the customer requested. It’s all done in-house (fun fact, Mil-Spec is now also doing upholstery for private jets). Virtually every non-upholstered surface is made from machined aluminum. That includes the steering wheel, climate control knobs, air vents, window switches, turn signal stalks, even the custom-made ignition key. They all look and feel superb with hefty weight and crisp edges. The toggle switches are a particular treat and return a light, mechanical click with each press. Some of them are a little tough to reach as a result of the Hummer’s strange interior layout, but that would be the case even in a stock Hummer. These aluminum pieces are a massive step up from the plastic rocker switches and air vents used on previous Mil-Spec Hummers.

The interior is more functional and comfortable, now, too. The shift lever has been replaced with a push-button array, and a new steering column is fitted, providing more hip and knee room for the driver. The gauges have been rearranged with the speedometer moved to the right of the steering wheel. This is because the speedometer was rather large and tended to be blocked by the wheel, so it’s more visible now. The climate control now has more fan and temperature adjustments for the air conditioning, rather than the original model’s two choices: on or off.

While Mil-Spec made major upgrades to the interior, it isn’t changing much about the mechanical parts of the standard M1, which continues with a 6.6-liter LBZ Duramax diesel V8 that puts out a healthy 500 horsepower and 1,000 pound-feet of torque. The customer ordering this M1-R wanted something more than standard, however. This LBZ engine was built by HSP Diesel, with a larger turbo, bigger injectors, improved cooling and more aggressive engine tune to make 800 hp and 1,200 lb-ft of torque. It’s matched with a similarly burly six-speed automatic transmission. This M1-R also was fitted with a Rod Hall Racing long-travel suspension and six-piston Wilwood brakes for all four wheels. And like regular M1s, it gets stronger axles than stock, ARB air-locking differentials and a Warn winch.

We got to drive the truck about a week after assembly was finished, and as such, the engine was still being broken in and running a preliminary tune. As a result, it wasn’t producing full power, and it was coughing out a fair bit of soot, but Mil-Spec says that all those issues would be sorted before the truck is delivered to the customer. Furthermore, we didn’t have an especially long drive, since the customer had some concerns about media driving their new baby. Still, we had enough time with it under varied driving conditions to get a good feel for the truck.

Compared to our last experience with a Mil-Spec Hummer, we wouldn’t call this better per se, but different, and enormously entertaining. Hitting the throttle on the M1-R yields quite a bit more noise than we remember in the previous M1, and most of it is good. The diesel engine emits a low, gravelly rumble, but the turbo is the highlight, sounding like a jet engine, getting louder and wilder as it spools up. It takes a fair bit of time for that spool up to happen, so the engine doesn’t feel super-responsive in town. It still gets around easily, but the big boost rush comes later. And what a rush. It comes on hard and pulls longer than in the standard engine. The juxtaposition of the acceleration and the size of the M1-R is giggle-inducing.

Rambunctious as the engine is, it feels even more wooly because of the handling and steering. The suspension setup is notably softer than the last Mil-Spec Hummer we drove. This is by design, as the goal was to make it more comfortable. And indeed it is, though it also leads to more body roll. The steering on this truck also felt considerably less precise and required a fair number of steering corrections. You’re definitely busier at the wheel than in most modern off-roaders. The good news is that the steering has a quick enough ratio and light enough effort that it doesn’t wear you out. In fact, it’s fairly easy to keep an eye on all corners of the truck, so maneuvering isn’t much more difficult than in any other full-size machine.

With the amount of work put into the M1-R, it’s no surprise it bears a hefty price tag: $412,000. That’s a big increase over the M1 base price of $299,500, and a big part of that was due to the upgraded engine and custom selections such as the exterior color, interior and long-travel suspension. But the standard truck still gets the already excellent 500-hp engine, and it will still get the same switchgear and leather upholstery (albeit in less striking colors and more subdued stitching). So we don’t think you would need to break $400,000 to get most of the fun by any means. Besides, while we don’t think Mil-Spec would say, “No,” to doing another M1-R if someone were willing to pay for it, Broekman told us that they weren’t planning on another one. They had fun working with the high-output engine, but they feel it’s about as much as they can do while trying to keep it emissions-compliant (Mil-Spec trucks are legal in all 50 states), so they’ll probably stick mainly to the base engine setup. In fact, Broekman said the company is keeping an eye on alternative-fuel powertrains, including electrics to possibly use in the coming years.

So the price is high, but there really isn’t anything else like it. It makes crazy noises, goes fast, and can do so just about anywhere. No Bentley or Lamborghini for the same money can come close to offering the same feeling.

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