Wehrli’s Modified GMC 3500 Denali Achieves Form and Function All in One Package

Photography: Wehrli Custom Fabrication

  • Wehrli Custom Fabrication (WCFab) is an Illinois-based truck accessories manufacturer that focuses on high-performance diesel applications and custom metal fabrication works.
  • Wehrli’s latest 112,000-square-foot facility provides ample space to grow into and hosts the company’s entire operations, including the robust manufacturing team.
  • The GMC Sierra 3500 Denali is the workhorse of the lineup, touting a 21,500-pound gooseneck towing capacity (31,760 as a dually) in factory form.
  • For Wehrli, its modified 3500 serves multiple purposes: a hauler to and from events, a testbed for the R&D of new components, and a show truck for the company’s beautiful components and powder coating work.

Gone are the days when a pickup truck could be described as a strictly utilitarian, basic vehicle. The modern equivalent—with air-conditioned leather seats, five-figure towing capacities, and six-figure price tags—like this GMC 3500 Denali, is decidedly different. They are equally proficient at being dependable work trucks as they are at making a luxury and performance statement. In many cases, the conscious decision to purchase one of these pickups over a similarly priced sports car—like a BMW M3—is dictated by the owner’s need for utility. But just because these trucks need to be workhorses doesn’t mean that an owner’s desire to mod has fallen by the wayside.


Long before the Wehrli brothers had driver’s licenses, they were cutting their teeth in the Powersports world; dirt bikes, ATVs, and snowmobiles were all part of Jason and Ryan’s lexicon. Eventually, the need to tow all of these toys gave way to their first Duramax. The desire to tinker soon bled into the truck world and the rest, as they say, is history. Today, Wehrli Custom Fabrication (WCFab) specializes in high-performance diesel upgrades and custom metal fabrication. Inside its 112,000-square-foot facility, the Illinois-based outfit designs and manufactures components for the truck community.


This Denali is a proud piece of its current fleet and serves multiple purposes: a hauler to and from events, and a testbed for the R&D of the aforementioned components. “By driving [the truck] both locally and on long road trips, we have been able to test our products in various driving conditions,” said Jason Wehrli. Indeed, this exact truck was the guinea pig for the majority of its 2020+ L5P Duramax product line. And since this Denali was a Swiss army knife for Wehrli’s company needs, it helped improve and refine each component to suit. “On long trips towing a trailer, reliability is of utmost importance,” added Wehrli. “This bundle of intake parts—the 4” intake kit (WCF100702) and 3.5” turbo horn (WCD100833)—eliminates weak points in the factory design that can contribute to lost power, boost leaks, and complete failures in hard-working and high-performance applications.” Wehrli’s Denali wears a handful of other complementary parts, like intercooler pipe kits on both the cold (WCF100381) and hot (WCF100365) side, a fuel filter housing kit (WCF100361), and a rear differential cover ((WCF100114), to circumvent factory shortcomings and provide headspace for performance add-ons. Thanks to a remote tuning package (and matching transmission re-map) from Calibrated Power Solutions, Wehrli’s Denali boasts over 150hp and 270 lb-ft more than a factory truck. It moves.


All of the added performance doesn’t come at the expense of the truck’s visual appeal. Wehrli prides itself on its finishing and its signature WCFab Red powder-coating work can be found throughout the Denali’s engine bay. If red isn’t your thing, this finish is reportedly one of 30 available hues within Wehrli’s catalog. “Our components, in addition to helping the truck run great, also look great under the hood. This Denali is just as much a work vehicle as it is a show truck for the company’s beautiful components and powder coating work,” Jason said. That attention to detail even extends underneath the truck; the WCFab Lower Splash Shield Kit (WCF100459)—which adds strength, coverage, and protection to the underside of the truck—is powder-coated to match, along with the front and rear lift components.

WCFab’s Fender Flare Billet Marker Light Delete Kit (WCF100390) is also a nice touch and cleans up the appearance of the front end perfectly. As far-ranging as Wehrli’s product range is, this Denali’s “form and function” execution was complemented by a generous helping of other mods. Cognito Motorsports suspension—a 4-6” lift kit, upper control arm kit, and extreme-duty tie rod center link kit—provide a comprehensive re-work underneath the truck. A set of Kelderman remote reservoir shocks, along with its four-link rear air suspension system, add leveling and robust damper performance when the truck does need to tow a hefty load. It was hard to imagine a scenario where a GMC 3500 truck could look small, but this Denali, as it sits, dwarfs a stock example.


Wehrli’s Denali strikes a fine balance between form and function. The truck is still as usable as ever; in fact, I’d argue that it’s even more capable than in stock form since many of WCFab’s components improve upon the factory recipe. Truthfully, Wehrli has staked its reputation on that improvement here. It was an even bolder call to use this truck as a testbed for its products when it, along with its payload, was so often called upon for time-sensitive company needs like shows or races. But it passed with flying colors. And that is why Wehrli has earned its steadfast reputation in the diesel community over the last 14 years. With this Denali, it continues to be a beacon of quality for that market and this truck, as it’s tastefully modified here, just proves it has no intention of slowing down soon.