Isn’t it funny how a single experience can change the direction of your life? Doug Barnes of Corona, California didn’t always have a cool GMC 2500. At one point, he was happy driving his Dodge Durango. That is until he went for a ride in his buddy’s Excursion. The Excursion, powered by a 7.3-liter Power Stroke benefitted from some mild performance modifications. The power amazed Barnes and he’s been hooked on diesel ever since.

It didn’t take Doug long until he bought a 2005 GMC 2500 HD with a Duramax soon after that memorable ride. Just five days after the purchase, Barnes began the transformation. It started with an Edge Juice With Attitude tuner and an intake and exhaust system. He did a couple more things here and there over the next few years, but eventually, Barnes got the bug to go big. That’s how it ended up with almost 700 horsepower and more than 1,000 lb-ft of torque.

Undercarriage Upgrades Under The GMC 2500

The truck has undergone a complete re-do since those early years, as the stock steering system was swapped out for a Red Head steering box, Cognito brackets, Rare Parts tie rods, and a Moog idler and pitman arm to beef it up. Dirty Hooker Diesel braided stainless power steering lines feed the system fluid to make it all go.

As for the suspension, the rear overload springs were removed, a 4-inch block was added, and then a set of Sulastic shackles were used to hang the rear springs. Caltrac traction bars from Calvert Racing help keep the rear axle from rotating under all that power. Up front, a Fabtech 6-inch suspension lift kit gets the truck’s nose up and provides plenty of wheel travel. With the suspension mods in place, Barnes was able to mount a set of 325/65-18 Mickey Thompson Baja ATZs wrapped around 18-inch Mickey Thompson Classic Lock wheels.

Body Beautiful

The interior and exterior of this GMC 2500 received some upgrades as well on the way to its present state. The instrument cluster features an Aqua Edition gauge overlay from U.S. Speedo and an Edge Insight CTS monitors the EFILive tuner for the engine. Ridge Runner Diesel Performance helped him set it up with five different custom tunes: Valet (something we think everyone needs), Stock Plus, Daily Driver (where it spends much of its time), Race, and Moonshine (Barnes took the Fifth on this one).

A plethora of illumination products adorn the truck’s exterior. LED halo projector headlights, LED turn signals, LED taillights, and an LED third brake light/bed light brighten up the scene. Further custom touches to the body include a Truxedo tonneau topping the cargo area that’s lined with a BedRug bed liner, and N-Fab triple step nerf bars and a Bestop TrekStep rear bumper step offer easier access to the interior and any cargo Barnes may be hauling.

2005 GMC 2500 Is A Gutsy Go-Getter

Transferring power to the axles is accomplished through a Stage IV transmission built by Inglewood Transmission. It uses a Precision Industries ML converter, a heavy-duty transmission fluid cooler from Inglewood Transmission, and a Mag-Hytech deep transmission pan to allow for extra fluid (to keep things cooler). The rear axle also has a Mag-Hytec differential cover.

Power production is the highlight of this rig, and the build started with a complete teardown. The block was decked and align-honed for the camshaft and crankshaft. All the machine work was performed by SoCal Diesel, and then it was reassembled by Robert Miller at MK Smith Chevrolet in Chino, California. The LLY received SoCal Diesel Stage 1 ported heads, SoCal Diesel .020-over cast and coated pistons (16.8:1 compression ratio), Carrillo connecting rods, a SoCal Diesel 3388 Hot Street/Tow camshaft, and an ATI/SoCal Diesel harmonic balancer. The entire rotating assembly was balanced, and the cam and crank were keyed. ARP head studs and main bearing studs were used on the block.

But it doesn’t stop there. The Garret GT4094VA turbocharger had its compressor housing extrude honed and polished, its exhaust housing extrude honed and Jet-Hot ceramic coated, and its heat shield Jet-Hot ceramic coated. The billet compressor wheel from Danville Performance was precision balanced, the aFe Power BladeRunner turbo mouthpiece was extrude honed and powder coated, and the EGR and PCV ports were plugged. In addition, the Merchant Automotive-sourced water pump had its gear and impeller TIG welded.

The Banks Power Technicooler intercooler with 3-inch boost tubes was powdercoated candy blue, the S&B cold air intake was painted white, and the LBZ 3-inch high-flow bridge (custom modified by Jason Wherli) and LBZ intake plenums were all powder-coated white. The ProFab Performance log-style headers and up-pipes were Jet-Hot coated, and a Diamond Eye 3-inch down pipe was coated as well. Both were also wrapped to improve heat containment. A 4-inch ProFab exhaust with the Cat deleted carries hot gasses to the tail of the truck.

Fueling this turbocharged 407 cubic-inch Duramax now is the job of an Air Dog 150 gph lift pump fed by a PPE billet fuel pickup. PPE ported fuel rail fittings (one on each inlet of the fuel rails) allow the fuel to flow into the Exergy Performance 60-percent-over fuel injectors.

Finishing Touches

To complete the under-hood decoration theme in this 2005 GMC 2500, Barnes went to the trouble of having all the engine brackets, mounts, and tabs powder-coated white. The alternator was disassembled and polished, as was the brass water diverter for the turbocharger. It’s quite a sight, but even more attention-getting when it’s howling at WOT.

The extremely modified Duramax cranked out nearly 700 horsepower and more than 1,000 lb-ft of torque when Barnes joined us for the Diesel Army Duramax Dyno Days. To see and hear the 2005 GMC 2500 roar, check out the video above. Stay tuned to Diesel Army for more great Dyno Day videos and truck features.