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2000 GMC Sierra Z71 Suspension - The Ultimate Z71Part 4: Sleeper Suspension From the November, 2008 issue of 4Wheel & Off-Road By Ali Mansour Photography by Ali Mansour
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Travel is what the Ultimate Adventure is all about. From the distance you drive to the flex of your rig, the greater the travel the tougher the components need to be. And when it came time to get our Ultimate Z71's suspension in order, we knew that the flagship vehicle could be nothing short of bulletproof. So far we've cut (Aug. '08), shortened (Sept. '08), and beefed (Oct. '08) our '00 GMC Sierra to help it better survive the grueling wheeling trip that is Ultimate Adventure. With the theme throughout being super sleeper, we knew we had to step it up in the suspension department so when this mild-looking pickup hit the trail it could crawl or blast over whatever terrain it encountered, even if it did look more out of place than Dolly Parton at a Metallica concert. Using readily available aftermarket parts we were able to keep our rig extremely low for stability, but still pull out more than 14 inches of front travel and 12 inches from the rear. I know you're probably glued to the awesome event coverage of the trip in this issue, but take a minute to check out the hard work and true craftsmanship that was put into the suspension by Mel Wade and his band of metal morphers at Off Road Evolution. From desert-racing technology and cutting-edge CAD designs to your basic run-of-the mill leaf springs, this GMC's suspension touches on all levels. For those of you who keep spinning the magazine in hopes of getting a better view of the truck's parts, go to www.4wheeloffroad.com and check out the photos we couldn't fit in the magazine.  Pairing modern technology...  Pairing modern technology with a proven performance suspension layout, Off Road Evolution designed, cycled, and mapped our GMC's front four-link suspension long before the first piece of metal was ever cut. Saving time and creating the best end product was the goal, and with all the files saved and each part equipped with a number, your Evolution coilover setup is only a phone call away.  We picked up our custom-etched...  We picked up our custom-etched engine tower and universal shock-tower pieces fresh from the laser cutter, and headed back to the shop. The shock towers are designed to weld directly onto the 1/2-ton's framerails, and we were able to position them high within the fenderwells, allowing us more adjustability for ride height and travel.  With the front axle moved...  With the front axle moved forward 6 inches, we notched the frame to allow the axle to cycle farther up. Once the notches were cut out we used our Hobart Iron Man 250 to box the frame back together for optimal strength and support.  Using Evolution's universal...  Using Evolution's universal four-link kit, we welded our brackets to the inside and lower portion of the frame. Outfitting each 1/2-inch-wall DOM link end with 1 1/4-inch Johnny Joints from Currie, we have full adjustment and control over our Dana 60.  Attaching the four links and...  Attaching the four links and utilizing a dual shear track-bar mount to the axle is Evolution's Dana 60 MOAB bracket set. Bolting the machined billet-steel bracket directly to the differential side of the housing, then welding the rest to the axletubes, we feel confident that our 1-ton front end is ready for some serious abuse.  Incorporating a set of 14-inch-travel...  Incorporating a set of 14-inch-travel 2.5-inch 9300 series Bilstein reservoir shocks up front, we were able to split the travel while still managing to keep the rig extremely low. Picking out the right coil rate is just as important as valving the shocks. We went with a 300 over 400 coil setup from Eibach that gave the truck a smooth highway ride and, more importantly, a stable feel on the trail.  Fitting the truck with a set...  Fitting the truck with a set of Bilstein bumpstops creates a type of secondary suspension, so if we ever feel the need to defy gravity, the landing won't be as tough. Another item to consider when setting up your suspension is how your track-bar angle coincides with your drag link. If the mounting points vary too much you may encounter a bit of bumpsteer. By moving our PSC steering gearbox 6 inches forward and matching the mounting angles, we ended up with a parallel system that is easy to control.  Borrowing a little Jeep tech,...  Borrowing a little Jeep tech, we mounted one of Currie's Jeep Wrangler TJ Anti-Rock sway-bar systems to the axle to gain stability both on road and off. One of the biggest benefits of the Anti-Rock system is that you leave the bar connected at all times, giving you the best of both worlds by eliminating the need for fidgeting around with disconnects and without losing articulation.  Steering 40-inch tires off...  Steering 40-inch tires off road can be a bit of a chore. So to give our tires a nudge in the right direction, we bolted on a hydraulic-assist kit from PSC. Complete with pump, ram, reservoir, and steering gearbox, the only thing you'll need is hoses and you'll be ready for the trail.  Though there are a variety...  Though there are a variety of ways to mount your ram, we built a dual shear setup, then nickel-welded it to the cast knuckle. This separates the loading forces from the tie rod and isolates the ram. And to protect the cylinder we built a slider/ram cage that will let us power and scrape the axle through the rocks worry-free.  Keeping our rear suspension...  Keeping our rear suspension under control is Off Road Evolution's universal Evo-lever system. Riding on a spindle and two bearings, the lever is connected to an adjustable link that mounts to the axle on one end and a shock on the other, in our case a Bilstein triple-bypass shock. Fully adjustable and found under dozens of desert-race applications, the Bilstein shock outfitted with the bypass tubes gives us the option of smooth control for low-speed wheeling like rockcrawling, or with the turn of a screw this truck can go blazing through the sand, mud, or desert.  Working with the Alcan replacement...  Working with the Alcan replacement leaf springs, the cantilever arm allows us to achieve a few very basic, but important, goals. One goal is increased travel over a traditional shock mount (we are netting right around 12 inches which is only limited by our springs) and the Evo-lever kept us from sticking the shocks up through the bed. This keeps the truck more of a sleeper and allows for more junk in our already shortened bed. Up-Sized
We had a few ideas on how tall our Ultimate Z71 would be, but were pleasantly surprised when we parked it between a stock 2WD GMC and a Chevy 2500 HD with a 6-inch lift and 37s. Though we haven't pulled the frame measurements to compare, we're thinking it's around 7 inches of lift and that's with 40-inch tires that can tuck fully into the fender!
Next Month
Check out how we hide a 15,000-pound Warn winch behind our stock bumper and manage to work through a few bugs and drivetrain issues as we bring it down to the wire before the Adventure. And for more on the UA Z71, slide over to the Web at www.4wheeloffroad.com.
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