The update likely arrives in 2018.

Mercedes-Benz’s engineering team are hard at work developing a big update for the venerable G-Class SUV, and now we have a brief spy video of a pair of them testing while towing trailers. Only one member of this duo actually moves briefly in the clip, but this is still a good opportunity to take a look at them.

Fans of the G-Class’ boxy aesthetic don’t have to worry about the luxury SUV suddenly gaining curves. The styling on this camouflaged example looks just as chiseled as on the current one. Previous spy shots indicate the biggest design tweak is the addition of about 4 inches (10 centimeters) extra width, and the change should make the front end look even more muscular.

While the exterior design remains nearly identical, there are massive changes underneath the skin. The G-Class reportedly has a new, more modern platform that could boast a massive 900-pound (408-kilogram) weight savings. The engine range shouldn’t change radically, but such a major diet should still yield significant performance gains. Fuel economy likely improves, too.

Mercedes’ product roadmap for 2017 is already available, and the updated G-Class doesn’t appear there. The omission suggests the SUV wouldn’t arrive before the 2018 calendar year. We'll likely see the German automakers testing more of them, too, which will possibly provide a better look at the improvements.

The G-Class’ off-road history goes back decades. The most recent facelift came during the 2016 model year and included some minor styling tweaks. The bigger change was the addition of Mercedes-AMG’s 4.0-liter biturbo V8 for the G500. For customers looking to get off the highway, Mercedes introduced the hardcore G500 4x4² (known as the G550 4x4² in the United States). The flagship of the range was the G65 AMG with a 6.0-liter biturbo V12 making a beefy 621 horsepower (463 kilowatts) and 738 pound-feet (1,000 Newton-meters) of torque.

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