1999-2006 GM 4x4 IFS Coilover ConversionPosted in How To: Suspension Brakes on October 27, 2016
If you have a lifted ’99-’06 GM 4x4, you’ve had to futz with torsion bars. In a stock application, the torsion bars work OK, but they add a lot of complexity and weight to your suspension system. When you add a lift kit, the required drop brackets generally hang down far below the frame, significantly decreasing ground clearance. JD Fabrication in Escondido, California, went to work on the GM IFS to come up with an affordable mid-travel steering and suspension solution. The company developed a simple weld-on coilover kit that replaces the clunky torsion bars and related crossmember bracketry. JD Fabrication specializes in go-fast long-travel suspensions for 2x4s and 4x4s. The company already offers a complete high-end long-travel IFS kit for the ’99-’06 GM 4x4 that provides up to 15 inches of wheeltravel. The new coilover kit increases wheeltravel to 11 inches. The kit also provides the performance and easy ride-height adjustability of a 2 1/2-inch-diameter King coilover shock with a remote reservoir. Here’s how it all comes together.
1. The JD Fabrication kit includes 2 1/2-inch-diameter, 10-inch-travel King coilover shocks, 700–in-lb coils, and custom shock ends that fit the factory GM lower A-arm. The truck height can be adjusted via the coil adjusting hardware.
2. Factory upper A-arms are replaced with heavy-duty 1.5-inch, 0.120-wall 4130 chromoly JD Fabrication arms. These feature 3/4-inch rod ends and 1-inch uniballs in place of the wear-prone rubber bushings and upper ball joints.
3. This truck has a 6-inch suspension lift. The JD coilover kit is available for ’99-’06 GM 4x4s from stock height to any amount of lift. Removing the torsion bars and related lift bracketry increased ground clearance under the frame of our truck by almost 5 inches.
4. The rubber shock bushings in the lower A-arms are replaced with uniballs pressed into aluminum adapters. A 17/64 drill bit and 5/16-24 tap are needed to drill and tap the holes for the set screws that keep the assemblies in place.
5. The factory upper shock mounts need to be removed from the frame. A grinder, torch, or plasma cutter can be used. Be careful when cutting in this area—there are several brake lines and wires nearby.
6. JD Fabrication supplies heavy-duty tie rods (top) to replace the tiny, failure-prone stock GM components (bottom). The JD Fabrication tie rods are made from 1.25-inch, 0.120-wall 4130 chromoly and feature quality 3/4-inch rod ends with stainless steel misalignment spacers and Grade 8 or better hardware.
7. The tie-rod end holes need to be reamed out to 5/8-inch, and the upper A-arm ball joint holes need to be reamed out to 3/4-inch to accommodate the larger hardware.
8. Problematic stock upper A-arm alignment hardware is replaced with lockout spacers. The A-arm alignment is now set via the 3/4-inch rod ends in the new upper A-arms.
9. Once the JD Fabrication upper shock mounts are tack-welded into place, you can mock up the coilovers to check for clearance. When everything looks good, you can fully weld the mounts to the frame. Clean off all paint and oil prior to welding or you’ll end up with a weak contaminated weld.
10. More wheel travel than stock is afforded by the new JD Fabrication steering bits and upper A-arms without going beyond the capabilities of the stock CV halfshafts.
11. The 2 1/2-inch King coilovers bolt into the new lower shock bearings and upper mounts. The reservoirs are then attached to the frame.
12. A removable cross brace is installed over the engine and connects the two upper shock mounts together for more reinforcement. The cross brace mounting tabs need to be welded to the shock mounts once clearances have been checked around the engine.