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Icon Vehicle Dynamics, Metal Tech 4x4 GX 470 Rear Suspension Install

May. 17, 2017 By Josh Burns
Our Lexus GX 470’s rear suspension is getting an overhaul thanks to parts from Icon Vehicle Dynamics and Metal Tech 4x4.

In our last story chronicling our Lexus GX 470 project, we focused on upgrading the front suspension with new coilovers and upper control arms from Icon Vehicle Dynamics. Aside from the performance upgrade afforded by our new Icon shocks, they also offer additional lift for the front end for additional ground clearance and suspension travel.

It’s time to shift our time focus on the rear suspension, where we’ll be swapping out the stock air suspension and converting over to coil springs with parts from Metal Tech 4x4 and Icon, and we’ll also be upgrading the rig with new Icon shocks and trailing arms.

After jacking up the vehicle, securely positioning a jack stand and removing the rear wheel, begin removal of the rear shock using a 17 mm socket on the lower shock bolt and a 17mm open wrench on the stem bushing nut and upper stem bushing. The rear shocks also have sensors that need to unclipped just like the front coilovers.

Our Icon Vehicle Dynamics Stage 7 package is a true bolt-on kit, as nothing needs to actually be modified short of a small hole drilled on each side of the frame for mounting the reservoir lines. Removing the rear air suspension system involves a few extra steps, however, so we wanted to break up the suspension upgrades into two parts to provide more detail on our installation.

The Icon 2.5-inch rear shock in the Stage 7 kit comes with a remote reservoir that houses additional oil volume to keep the shocks cool during intense off-road use. The Icon shocks also include the company’s CDCV upgrade, which is controlled via a dial on the reservoir that allows for the fine-tuning of the compression damping.

The air suspension system of the GX 470 is controlled by air bags mounted to the rear axle, one per side. The air bags themselves aren’t too difficult to remove, but you’ll have to decide how much of the system you’ll want to keep intact if you want to leave the option open to return to it down the road.

With the GX 470 quietly growing in popularity (a trend we expect to continue), there are a number of coil conversions out there. Rear springs are included in our kit from Icon, and since we’d be adding a Metal Tech 4x4 rear bumper and spare tire carrier, we opted for the heavier 3-inch coil springs to compensate for the added weight.

Since we’d be removing the stock air suspension system from our GX 470 and replacing it with coil springs from Icon with no plans to turn back, we went ahead and snipped the air lines prior to removal.

Removing the air bags is relatively painless provided you know how they come off. The air bag base is attached at the axle and that’s pretty clear-cut, but atop the bag there’s a u-clip connection that is secured on a nipple-mount. The clip can be tricky to remove if you’re not aware of it, but once you locate the clip it can be popped off with a flat-head screwdriver or similar tool

Having the springs to replace the air bags is one thing, but there needs to be something to actually hold those springs in place. Fortunately, Metal Tech 4x4 offers a simple solution for doing so, with one option that includes the hardware necessary to hold the spring in place on the rear axle and another that includes both the hardware and what’s called a spring isolator, which is a large piece that looks very much like a bump stop that actually rests inside the coil spring and then sits just between the spring and the frame of the GX. Metal Tech 4x4 makes the process easy by offering a kit that includes the spring isolator and spring retainer hardware, though there is the option to source the isolator yourself (either new from a dealer or from a junkyard). Although we sourced the spring isolator, the complete Metal Tech 4x4 kit is the best bet for most because it makes the process simple.

The upper (top) and lower (bottom) trailing arms included in our Icon suspension kit are more durable than their stock counterparts because of their sturdy construction, but they also allow for the adjustment of the pinion angles. Improper pinion angles can lead to driveline vibrations and premature driveline and u-joint failure.

With the air bag removed, we shifted our focus to the trailing arms before putting the new Icon springs in place. The GX’s upper trailing arm comes off first. Note: the stock piece has a large sensor attached to it that works in conjunction with the air suspension to sense ride height, and since ours is going bye-bye so is the sensor. Remove the stock trailing arm with a 17mm socket or wrench and retain the stock bolts, as they will be reused.

The new billet upper trailing arms from Icon are considerably more durable than the stock arms.

Before the new Icon arm goes on, you’ll want to initially adjust its length to match up with the outgoing stock arms. The easiest way to do this is to set the Icon arm on top of the stock upper trailing arm to make sure the bolt holes line up. Adjust the new Icon arm length as necessary to ensure a proper fit.

After ensuring the new Icon arm is the proper length, install it using a 17mm wrench and reusing the stock bolts and nuts.

Our spring conversion is possible thanks to this kit from Metal Tech 4x4, which offers two options for the conversion with one that includes the hardware necessary to hold the spring in place and another that includes both the hardware and the spring isolator - the large bump stop-looking piece that will sit between the spring and the frame of the GX.

These Icon springs will be replacing the air bags on our GX 470, and since we’ll be installing a Metal Tech 4x4 Pegasus rear bumper and spare tire carrier, we opted for the heftier 3-inch springs (part# 52800) from Icon. Note: The spring is sitting on the new spring isolators and the Metal Tech 4x4 coil conversion hardware is resting just to the right.

The Metal Tech 4x4 hardware to hold the spring in place mounts directly to the preexisting hole on the rear axle where the air bags previously resided.

Before installing the spring itself, we shifted our attention to the lower trailing arm and began by removing the stock arm.

Once the stock arm is off, just like the upper arms the new Icon lower arm needs to be the same length as the outgoing stock piece for the initial installation. Measure and make adjustments (again, the easiest way is to set them on top of each other and line up the bolt eyelets).

Once the lower control arm is installed, we wrangled the spring in place.

Reconnect the brake line to the new Icon lower control arm that is pre-drilled to accept the stock bolt.

When it comes to installing the rear shock and remote reservoir, Icon includes hardware to mount the metal bracket for the reservoir along with the clamps to help hold it in place. On the passenger side (shown), the reservoir mounts simply thanks to the stock frame hole being accessible toward the rear of the frame. On the driver’s side, it’s not quite that simple (see next image).

Since we swapped out the airbags for springs and had no intention of reusing the stock air equipment, we decided to remove both the air compressor and reservoir tank assembly pieces from the driver’s side of the frame. Not only would these parts be unnecessary moving forward, they were also in the way of mounting the Icon shock reservoir on the driver’s side.

The rear shock is ready to be installed. Keeping the padding on the reservoir will protect it from dings. One of the coolest aspects to these Icon rear shocks is the built-in bump zone that increases compression valving in the final two inches of travel to help reduce bottoming out.

Removing the air suspension parts exposes a stock bolt hole to mount the reservoir – just like the passenger side. Icon suggests mounting the reservoir for the rear shock along the frame toward the rear of the vehicle.

To secure the reservoir line a small hole needs to be drilled into the frame for the line mounting bracket.

Once everything is in place, double check that everything is tight one last time and reinstall the wheel. Icon suggests rechecking bolt tightness after 100 miles.

Overall, the rear suspension upgrades we performed were pretty straightforward. As we noted in our front suspension story, we do not have a KDSS-equipped GX, which makes things a little simpler since there’s a few less parts to worry about. We did decide to remove the air suspension components entirely, as we have no plans to convert back to the system. For this installation, a competent garage mechanic can tackle it in roughly half a day, but as always, if it seems too daunting a task your local 4x4 shop can knock out the job in short order.

MORE GX 470 STORIES
Icon Vehicle Dynamics Front Suspension Installation

Luxury Off-Road: Why We’re Building a Lexus GX 470

SOURCES
Icon Vehicle Dynamics
951/689-4266
IconVehicleDynamics.com

MetalTech 4x4
503/822-1111
MetalTech4x4.com

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