PART FIVE: UPPING THE STANCE
Part Five of our ongoing 2012 LML Duramax saga finally digs into to making this thing look better while offering a little more off-road versatility with a leveling kit, new shocks and some new hybrid all-terrain tires on matte-black 20-inch wheels. The factory 18-inch wheels had virtually brand-new Michelin tires on them, but this shimmering graycolored truck was lacking some serious style and it’s amazing how far the right wheel/tire combo can take a truck.
In the earlier parts of this build—see the last four issues of Diesel World for complete in-depth information—we took this higher-mileage used Silverado 2500HD from a bone-stock truck with a camper shell to what you see now. We’ve upgraded the intake and exhaust with a Jammer 2 kit from Edge Products and installed new tuning and an in-cab color monitor for better mileage, throttle response and power with the Edge Evolution CTS2. Part Two brought better airfl ow with a 3-inch high-fl ow intercooler tube from Deviant Race Parts, and we ditched the camper shell in exchange for a Bestop EZ-Roll tonneau cover so we can hook up to a gooseneck trailer while still being able to protect stuff in the bed. In Part Three we installed the FASS Titanium 165gph fuel lift pump to help with fuel fi ltration and take some load off the factory CP4 injection pump. Last month was general maintenance time with a transmission service for the 6-speed Allison, swapping out the fi lters for new ones and adding a deeper transmission pan and a transfer case brace from Merchant Automotive. While the trans pan was off we also added a Shift Solenoid fooler from Deviant Race Parts to up the line pressure within the transmission so it could better handle our new horsepower and torque levels.
Now that we’re all up to speed, let’s get back to this month’s upgrades. Installing a front-end leveling kit on the 2011+ body style seems to be more relevant than with previous model years because the 2011+ trucks sit taller in the back. Rather than having a 2-inch rake front to back it’s a 3-inch rake, which in our professional opinion doesn’t look that great. Since we wanted to swap out the wheel and tires for something more aggressive-looking from Mickey Thompson, we had to address that low front end. The Stage 3 Leveling Kit from Kryptonite Products of Diamond Springs, Calif., was the perfect answer.
This system can safely raise the front of your truck 2 inches without hurting CV axle or ball joint angles, so it’s not recommended to go any further than this without doing a full lift kit, which would replace the front steering knuckles and change the torsion bar mounting locations. With a 2-inch leveling kit the 2011+ trucks still won’t have a completely leveled stance, so Kryptonite does offer a 1-inch drop shackle that can be installed on the rear leaf springs to bring the back end down and give you that complete leveled look. It’s something we’ll most likely be adding in the near future when we do some more rear-end work. For now, the 2 inches up front was enough to get the required clearance for our new tires.
This truck is used mainly as a daily driver and will see a lot of highway miles while towing through the summer months, but it will also get to see some off-highway use, which may lead to a few muddy mountain roads. Living in Utah, it’ll also see snowy commutes to work, so a good all-terrain tire can offer much better results for all-around use than the factory highway treads would. Picking one that can offer everything—great off-road traction and low highway noise while also looking great—can be tough, but lucky for us truck owners tire manufacturers have paid attention to our wants and needs and developed what they refer to as the “hybrid” terrains. The Mickey Thompson Baja ATZ P3 is one these so-called hybrids that combines a design suited for low highway noise and long tread life with an aggressive mudterrain tread for the ultimate in off-road traction. The ATZ P3 has a taller lug profile for excellent lifespan (45,000-mile limited warranty) and good traction offroad. The silica-reinforced tread compound offers great wet road performance, longevity and cut/ chip resistance.
For this truck, we went with a 285/55R20 tire—in Load Range E, of course, so we can continue towing heavy. To mount these up on the truck, we obviously had to replace the stock 18-inch wheels with a 20-inch variation. Again we turned to Mickey Thompson for the 20×9 SD-5 wheel just released for the 2011+ GM 8×180 lug pattern. The SD-5 wheel has a nice 5-spoke design with a matte-black powdercoat and machined accents for great contrast that looks awesome on just about any color truck. The wheels and tires were dropped off at Lynn Wood Automotive in Clinton, Utah, to be mounted and balanced. They had to install some new tire pressure sensors and ordered some new splined black lug nuts for us as well. We finished off the leveling kit install in about five hours and drove right over to the tire shop so the new shoes could be installed and the truck could be aligned. Even though we’d marked the cam bolt locations before swapping out the upper control arms, the new geometry of the taller stance had thrown the front camber way off. The Lynn Wood Auto techs had to make some adjustments to get everything within spec so we’d be sure to get the best tread wear and tire life possible from these ATZ tires.
Once the alignment was completed and the lug nuts and been torqued to spec, of course we had to go out for a test drive. As aggressive as these tires look, you’ll be impressed with how they act on the asphalt. They don’t give you the heavy steering feel you’d expect and the tread noise is much quieter than anticipated on the freeway at 75-80 mph. The balance seems to be spot-on as well, which can be a challenge on a big, heavy wheel/tire package, as there is no shimmy or vibration on the freeway (thank you Lynn Wood Auto). We do expect to see our fuel mileage drop some due to the added weight and rolling resistance, but that will remain to be seen until we get some more miles racked up. The tires haven’t had a chance to see the mud just yet, but on a 45-mile snowy morning commute before the plow trucks were out they worked extremely well in the snow and icy road conditions.
Next month we’ll get back to some performance upgrades and will be doing some more fuel system work. We’ll replace the fuel tank with a larger Titan tank and install a new returnstyle fuel sump from Deviant Race Parts. We’ve got a lot more to upgrade and replace after that though, and we’re looking forward to showing you what these trucks are capable of with the right parts and some time in the garage.