I Towed 20,000 Pounds up the Legendary Davis Dam Grade. Here’s What It’s Like

Iconic roads across the United States have earned their reputations for one reason or another. If we’re talking about the Pacific Coast Highway that runs up and down California, it’s known for its views; if we’re talking about Tail of the Dragon over on the Tennessee-North Carolina line, it’s famous for having 318 turns. Those routes are in the syllabus of Becoming a Car Person 101. But what if you’re into trucks? Trails like the Rubicon and Black Bear Pass have their place, for sure, but there’s only one road where trucks are legally required to prove their salt when it comes to working. That’s the Davis Dam grade.

See, before a company like Chevy or Ford or Ram can claim their truck is capable of towing 35,000 pounds or more, they have to prove it here. Because of the climate and topography that defines this section of Arizona State Route 68, it’s become the mandatory test for automakers to obtain their SAE J2807 certification. That might sound boring, but it’s a mighty task. To be certified, trucks have to pull their maximum weight rating up the 11.4-mile pass in 100-degree heat with the AC on full blast while maintaining 40 mph (or 35 mph for duallys). It’s not a walk in the park by any stretch.

After hearing about the Davis Dam grade for years, I finally drove it last week in a 2025 Ram HD with nearly 20,000 pounds behind me. I can confirm—it’s a beast. But when you’re in a rig as capable as these new heavy-duty pickups, it’s almost boring … which is what you want when you’re pulling around so much weight. It could very quickly be the opposite if the rig you’re in malfunctions.

The climb started as I drove over the Colorado River, going from Nevada into Arizona. There’s not much out there besides a few casinos with overwhelmed air filtration systems (ask me how I know). But as you start to ascend from 541 feet above sea level in Bullhead City, the road just goes up and then up some more. At 50 degrees Fahrenheit, it was fairly brisk out when I was there, but cars were still pulled off to the side with their hoods up. If it’s enough to put a hurt on a Corolla, you can imagine how big of a task it is for a truck towing a trailer that weighs more than a regional airliner jet.

The speed limit actually increases as you travel further up the grade. It starts around 45 miles per hour, and there are some big sweepers to go along with the steep incline. Signs everywhere warn drivers of the five-mile-long 6% grade, though some have speculated it’s even greater than that at some points. Anyone who’s been to San Francisco has driven steeper streets, but not at speeds like this, and likely without a big ol’ trailer behind them.

By the time you reach the 55-mph zone, the road levels out for a bit of reprieve. It doesn’t last long, though, so this is your best shot at getting a run for the next climb. The Ram 3500 that I was in kept up through here just fine but as it transitioned to a 65-mph zone, I had my foot on the floor to keep from dipping below the posted limit.

Now, we have to stop and think about that for a second. This is a truck with 1,075 lb-ft of torque—just an absolute beast—and even on a cool day without all the accessories running off the engine, the speed was limited not by my boot but by gravity. And sure, 19,000-and-change pounds is a lot of weight, but it’s still literally tons below what the truck is rated to pull. These details perhaps paint the clearest picture of just how tough this test is. Double the ambient temps, throw on a lot more weight, then crank the AC and you have a torture chamber for trucks in the Arizona desert.

And still, modern trucks can do it. It’s amazing. Even though I was still way beneath the Ram’s max tow rating, I was impressed to see the coolant gauge stay put below 210 degrees Fahrenheit while the trans temp never went past 160 degrees. I’ve drank coffee hotter than that!

Crossing the peak at Union Pass, which sits at roughly 3,500 feet of elevation, feels like a win. Just over the hill is a miles-long view of what they call Golden Valley, which gives good perspective of how high up you are. The best way to grasp that, though, is by flipping around and running down the grade.

This tests entirely different systems on a truck—namely, the brakes. Bright yellow signs line the roadside, warning drivers to use low gears. There are runaway truck ramps with ultra-soft gravel meant to absorb and slow down heavy rolling rigs. The turns feel twice as sharp as you’re going back toward Bullhead City with a big trailer running you down. Rely too much on your friction brakes and you could be hurting in a hurry.

That’s why exhaust braking is crucial on the downhill run. Whether you drive a modern diesel pickup that engages the function through a touchscreen or you’re in a semi with a Jake Brake that you flip on to wake the dead, this is the time to use it. (In case you’re unfamiliar with exhaust brakes, they work by opening the exhaust valves slightly during the engine’s compression stroke. This allows the engine to absorb the power rather than distributing it to the rest of the drivetrain. You’re then able to control your truck’s speed without using the friction brakes, or without relying on them so heavily at least.)

If you’re used to pulling a trailer through the Rockies, then this will feel familiar; if you’ve only ever towed across the Midwestern plains, then you better use your noggin. It’s far from the steepest descent—I don’t want to exaggerate—but any truck and trailer is one equipment failure away from a bad day running down the Davis Dam grade.

No picture or video I share can really do it justice, but then again, I’m not here to prove anything to you. I’m just sharing my experience on one of those now-iconic roads that hundreds of automotive engineers in the U.S. have tested at. If your car or truck was built after 2008 and has a listed tow rating, then this is where it got it. To me, that’s pretty cool.

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