Brian Randall — owner of Randall’s Performance in Gladstone, Illinois — wanted to put together a demo truck for his shop to show off the products they sell and install. Rather than rework an older truck, he wanted to be on the cutting edge — so he purchased a brand-new 2015 Chevrolet Silverado 3500HD. As nice as the all-new 2015 Chevy HD trucks are, Randall and his crew saw a great deal of upgrade potential. With the ink on the sales agreement practically still wet, Randall and his crew picked up their wrenches and got to work on the new truck.
The first step was to improve the truck’s appearance. The crew at Randall’s installed a 4-inch Fabtech suspension system complete with new Uniball front control arms and Fox Racing Shox on all four corners. To set the stance, they added a 1-inch lift block in the rear while turning down the front torsion bars to provide 3 inches of lift instead of 4. A set of One Up Offroad traction bars prevents axle wrap and keeps the rear axle tracking true, while Cognito idler and pitman arm braces beef up the steering system and keep the big Chevy pointed in the right direction.
With the truck lifted, the build team was able to fit more rubber underneath in the form of a set of LT305/55R20 Mickey Thompson Baja ATZ P3 tires wrapped around chrome American Racing 20×9 AR708 wheels. They installed a set of Luverne textured mudflaps to protect the paint from rocks and other road debris that might be thrown up by the aggressive tires. Luverne stainless steel step tubes ease ingress and egress while improving the look of the truck.
The interior of the all-new Silverado is nice enough that Randall saw no need to make any dramatic changes. He installed a set of WeatherTech molded floor mats to protect the carpet during harsh Illinois weather, and since the truck will be hauling his kid and his dog, he installed a Covercraft rear seat cover to protect the leather. Augmenting the factory gauge cluster is an Edge CTS monitor mounted next to the driver’s side A-pillar. Randall then installed Edge EAS attachments to monitor primary and secondary turbo boost through the CTS. Randall and his crew also installed a Fuel Lab 100-gps pump and filter system and set it to 18 lbs to feed the soon to be upgraded Duramax fuel system.
Randall plans to use the Chevy as a work truck as well as a demo truck, so he installed a B&W gooseneck hitch under the bed, with a Truxedo Lo-Pro soft tonneau cover to keep the bed protected and out of view of prying eyes. The Truxedo cover butts up against a Better Built diamond-plate aluminum storage box at the front of the bed.
Once the crew at Randall’s finished modifying the suspension, exterior and interior, they shipped the truck to Jason Wehrli and his crew at Wehrli Custom Fabrication in Sugar Grove, Illinois, for a compound turbo kit. WCF used a large BorgWarner S475 turbo with the LML’s factory VVT turbo, a combination that builds boost quickly and makes strong top-end power. The fuel system was upgraded with a WCF kit that replaces the factory CP4 with an Exergy long-stroke 10mm CP3 high-pressure pump, delivering more fuel through the stock injectors.
In developing the compound turbo kit for the 2015 GM trucks, the crew at WCF fabricated new intercooler boost tubes as well as hot and cold piping to the turbos. The intake charge is drawn into the remote-mounted S475 turbo through an aFe Pro Dry S cone filter before being sent to the inlet of the factory turbo in the valley. From there it’s compressed once again before being routed to the intercooler and returning to the intake manifold through new powder-coated boost tubes. On the exhaust side, spent gases first flow into the factory turbo and then to the S475 through heat-wrapped piping. The exhaust is expelled through a 4-inch diameter Pro Flow stainless steel exhaust system that terminates behind the passenger side rear wheel with a polished 6-inch diameter tip.
To make room for the BorgWarner turbo, Wehrli and his crew fabricated a custom overflow tank and removed the passenger side battery. The team then turned to Motor Ops in Mississauga, Ontario, for an EFILive AutoCal loaded with custom tunes to get the most performance out of the otherwise-stock Duramax. When the truck was run on a Superflow chassis dyno, it put down an impressive 611 horsepower with 1,092 lb-ft of torque to the rear wheels.
While the turbo kit was being installed, WCF also made some modifications to the Allison transmission. They installed a Sun Coast GMax kit with upgraded clutches, steels and pistons, and a Goerend Transmission triple-disc torque converter with a billet stator. The transfer case still drives the front axle through the stock driveshaft, but the rear wheels get their power through a steel one-piece shaft from Zaiser Fabrication. The upgraded driveline gives the Chevy the strength to handle sled pulling and other hard work that Randall plans to tackle.
Brian Randall set out to build a truck to show off the parts, products and manufacturers offered at Randall’s Diesel Performance—and we have to say that he succeeded. From the outside, he has a sharp-looking Chevy that isn’t ostentatious; inside the truck is well appointed and comfortable, a perfect environment for customers to try out his shop’s work. But subtlety gets thrown out the window when the hood is opened—two turbos, custom plumbing, and a clean installation scream “POWER!!” The all-new 2015 Chevrolet Silverado is a great truck right off the showroom floor, but we think Randall’s and Wehrli’s have made it just about perfect. DW