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Suspension Facts & Tips - Chevy Brand Pages - 4-Wheel & Off-Road

David Kennedy Contributor 2002 Chevrolet Tahoe front Right View Photo 9056502

Face it. Nobody would buy a 3/4- or 1-ton truck to take wheeling if you could get a big-block, diesel, or full-floating axle in a 1/2-ton. We've even been guilty of it ourselves! So until the day comes when you can check off the Allison/8.1L option on a 1500 Silverado, we're all going to buy these huge trucks to get the drivetrain we want in a package that's more trailer-ready than trail-ready. Fortunately, the aftermarket has been right on top of this 3/4-and-up truck trend and has come to market with everything the 1/2-ton guys have been enjoying on their wimpy little trucks. We wheeled down to Rancho's prototype shop in Long Beach, California, to check out its newest offering for GM's biggest truck.

There is no way around it. This 4-inch lift doesn't let you fit 35s like the competitions' 6-inch kits do, but it could be the perfect combo for the guy who wants bigger tires on his tow vehicle or work truck without any downsides. You can take comfort in knowing that the suspension engineer who designed this kit owns one of these trucks, so you can be sure he had your best interests at heart.

The factory ride quality will only improve with the Rancho 4-inch kit as the springs and torsion bars remain, but the shock tuning is vastly improved. If you choose the RS 9000 five-position adjustable shocks you can dial your own ride characteristics to match your needs. We didn't get to romp on this kit, but expect the one-piece subframe to hold up for a lifetime of use, as there is very little to come loose. Think you're ready to step up to the 4-inch lift plate but need more information? Rancho's world class installation manual is available for you to download at www.gorancho.com.

bSuspension Quick Facts
•4-inch lift
•Fits '99-and-newer 1500HD, 2500, 2500HD, 3500, 2500 Suburban, and Avalanche 2500 trucks
•Fits 285/75R16 tires on 16x8 rims, 41/2-inch backspacing
•Stock wheels will bolt on
•Rancho's instructions suggest 41/2*of caster, 0* to 0.3* of camber, and 0.1* to 0.2* of toe-in for best handling

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01. The front suspension is lifted with cast-iron drop-knuckles designed by Rancho to retain the factory suspension and steering geometry. These new knuckles have become the rule more than the exception and are the best thing to happen to IFS lift kits. They allow the 4-inch kit to retain the factory mounts for the upper A-arms and all of the steering components. The original brakes still bolt right up. Alignment shops prefer this design to kits that drop the upper A-arm mounting points and steering because it is easier to set them to factory alignment specs.

02. A one-piece subframe made from DOM tubing mounts the lower pickup points of the front suspension. When installing its kit Rancho recommends the front differential assembly be mounted to this new subframe before lifting the entire assembly up into the truck. This one-piece design can be trickier to install than the typical two-piece lower subframe, but makes for a very strong kit once in place. If you were installing this kit in your driveway you'd need to set this assembly on at least two floorjacks. Professional shops with a lift can use a transmission jack or even a rollaway cart, and lower the truck onto the subframe.

03. Like all GM IFS lifts, the Rancho 4-inch kit requires you to cut the original rear differential mount off the frame (the instructions show you exactly where to cut) and box it with the supplied steel plate. The differential now bolts to the Rancho subframe with the original hardware. No front driveshaft or exhaust modifications are necessary with this kit.

04. The new front differential mount (the old one must be cut off) is shaped like a boomerang and bolts to the aluminum case and then to the subframe with a new urethane bushing. When removing the five bolts from the differential case some oil may leak out. If it does be sure to check the fluid level when the truck is back on the ground and add any if necessary. Depending on how your HD truck is equipped from the factory you may or may not have a steering stabilizer. Rancho offers an optional unit that will bolt up to the frame and factory centerlink if your truck didn't come with one.

05. Rancho developed its 4-inch kit to be used with 285/75R16 (32x11.50) tires on a 16x8 wheel with 41/2 inches of backspacing. If you want to run 35s with this kit (we wouldn't recommend it), you'll need to add a 3-inch body lift or trim a lot of the inner fenderwell and maybe even part of the front bumper. The GM wheel openings are not very accommodating of larger tires, so at the very minimum expect to trim the front air dam back 3/4-1 inch per side. This isn't a big deal and looks factory even to the trained eye.

06. Rear lift height is gained the old fashioned way with lift blocks, longer Rancho shocks, new U-bolts, and new bumpstop relocation brackets. Because the stock rear springs are retained, factory load and towing capacities are maintained. The adjustable RS 9000 shocks used here are a big improvement over the factory shocks because you can soften them up when unloaded to remove a lot of kick from the rear suspension. Just dial them back up to get the load control back when you head to the lake with the boat or a bed full of toys.

07. Rancho suspension engineers have a shock dyno right in the prototype shop to help them develop dampening curves for lifted trucks. After a testdrive, a shock can be cycled on this equipment to help the ride and drive engineer decide whether the shock is too firm or too soft under any condition. The engineer that designed this kit runs the shock on position three front and rear on his personal truck, but the RS 9000 shocks let you tailor the ride to your own liking.

08. Stay away from RTI ramp competitions with any GM HD truck--they're just not made to flex. That doesn't mean you have to keep these late-model 4x4s on the street. The optional, integrated Rancho aluminum skidplate will protect the frontend components through the roughest IFS bashings. These Duramax and 8.1L-equipped trucks have a ton of power, and with a Rancho lift and larger tires you can put that power to the trail, not just to the trailer.

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Suspension Facts & Tips - Chevy Brand Pages - 4-Wheel & Off-Road

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