5th Generation 4Runner Suspension Overview

4Runner Suspension Terminology and Guide – Toyota IFS Overview Guide

Front 4Runner Suspension Terminology

• Coilovers
• Remote Reservoir
• Shock Wraps Neoprene Coil-Over Shock Protection Covers
• Secondary Shock Hoop Kit
• Struts
• Upper Control Arms
• Ball Joint
• Ball joint UCA Cover Kit
• Lower Control Arms
• Stock Lower Control Arms Replacement
• Lower Control Arm Skids
• 4Runner Lower Control Arm Cam Tab Gussets
• Differential Drop Kit
• Body Mount Chop
• Limit Straps
• Sway Bars
• Long Travel Polyurethane Bushing Kits
• Sway Bar Relocation Blocks
• Upper Coil Bucket Tower Gussets

Coilovers

Coilovers short for  “coil spring over shock” is a suspension device that consists of a shock absorber with a coil spring encircling it. The shock absorber and spring are assembled as a unit prior to installation and are only replaced as a unit if the shock absorber has sprung a leak.

Coilovers provide damping without torsional loads which is a huge benefit. Some coilovers offer adjustment of ride height and preload, using a simple threaded spring perch similar to a nut. That is great if you’re wanting an adjustable ride height for your 4Runner.

There are more advanced adjustable coilover systems available though, they use a threaded shock body, along with an adjustable lower mount for ride height adjustment. They also have an adjustment knob in some cases that is used to adjust damping. The stiffness can be changed by switching the spring for one with a different spring rate so you can adjust your 4Runners ride if it’s too stiff or not stiff enough.

There are two types of coilovers made, full coilovers and slip-on coilovers. The full coilovers are matched up with a shock from the factory, while slip-on coilovers are typically just adjustable springs.

There are benefits to coilovers along with disadvantages like all things though.

Benefits

• Coilovers provide tight packaging for shocks and springs
• Assembly line installation is easier with distinct packages
• Easy replacement with aftermarket coilovers
• Aftermarket coilovers can offer many adjustments including ride height

Disadvantages

• Increases shock wear due to spring sideload
• Increased shock bushing wear
• More expensive to manufacture than separate shock and spring

Remote Reservoir

Remote Reservoirs are an external reservoir that increases fluid capacity within your shock. This increase in capacity helps lower fluid temperature, Which offers the ability to blast over rough terrain without experiencing shock fade. For those who don’t know, shock fade is when the shocks virtually stop working, they then do not provide any resistance and control to movement.

There are two kinds of remote reservoir shocks. First up there are Piggyback-style shocks, they have the remote reservoir mounted directly to the shock body. The second option for a remote reservoir is when it’s attached by a high-pressure hose, it allow’s you to mount the reservoir wherever you choose.

Remote reservoir-style shocks are built and tuned to improve your vehicle’s ride and performance over a wide variety of terrain and conditions. The reservoirs are really a necessity if you plan on driving long distances on extremely rough tracks, or if your 4Runner is fully loaded when touring. Shock fade on a loaded vehicle can become extremely dangerous when driving at higher speeds, which could potentially become a life-threatening issue.

Remote Reservoirs have many advantages for those who offroad or put stress on their shocks. Inside the reservoir, a floating piston separates the nitrogen from the oil, preventing, aeration similar to the design of the shock itself. A big advantage is the previously mentioned increased oil capacity, Other than it aiding in cooling and preventing shock fade for the most part it increases the service life of the oil. Another big advantage is the added gas volume, It helps the compression and rebound valves to retain consistency under the most severe off-road terrain or other severe surface conditions.

While remote reservoirs might seem like they wouldn’t be as durable as the main shock they are. The bodies consist of a thick high-tensile steel pressure cylinder, which is plated for corrosion resistance. Inside, they are designed to be highly durable as well. They are built to be just as strong and even sometimes stronger than your main shocks. The reason they have to be made durable is due to them not being protected by the spring in most case’s unless you have a Piggyback reservoir.

Benefits

• Increased oil capacity
• Can allow easier fitment of long travel shocks
• Helps prevent dangerous Shock Fade
• Most are rebuildable at home

Shock Wraps Neoprene Coil-Over Shock Protection Covers

Shock Wraps are a must have for vehicles that see extreme weather conditions. They are also a must-have for your 4Runner if you do a lot of Dirty/Muddy Off-Roading more often then not. These neoprene coil over shock protection covers offer an added layer of resistance keeping dirt, mud, grime, snow, harsh road salts/spray’s, and any other harsh conditions.

They also prevent rocks from getting to the shock shafts or seals. This added layer of protection helps prevent damage like shaft pitting & cut seals that require you to have your shocks rebuilt prematurely. Most wraps use velcro and can be put on or taken off in seconds, some do use zippers instead of velcro though. Most also are designed with an elastic banded end to have a nice tight fit to give you the most protection possible.

There are plenty of other advantages to shock wraps as well. One of the best feature’s is they protect from anything hitting your coil springs and chipping the paint. While you may not care if they get chipped up appearance wise, it can lead to the chipped area corroding.

It also provides great protection to your coilovers appearance, many companies including icon use an anodizing that looks great but it can easily be ruined by road salt and other chemicals used to melt snow/ice in the winter. Shock wraps also help prevent gunk and grit from building up in the threads of the shock body, this will allow to easily and safely adjust the pre-load on your coil overs should the need arise.

Benefits

• Added Protection for Coils Springs, Shock Shafts, Shaft Seals
• Can be installed or removed in seconds without removing shocks from the vehicle
• Additional layer of protection from rocks, road elements and other harsh condition’s
• Typically they cover from upper coil adjuster nut down to lower spring perch

Secondary Shock Hoop Kit

The secondary shock hoop kit allows you to do what it say’s add a secondary front shock. Why would you do this you might ask well there are a few different reasons. But before we get into them these kits are great for avid offroaders.

A dual shock system adds increased damping ability and increased control going fast. Additionally, it allows you to run a bypass shock in the secondary position, which is position-sensitive (built in bump zone) and has independently adjustable rebound and compression.  The cost is high, and the kits are typically complex, but it increases performance by a lot in those areas where you can offroad with a little speed.

A dual shock set up is also a great addition to your 4runner if you’ve managed to overheat your shock’s with a remote reservoir. While that would be hard to do it is possible, especially if you offroad with your rig fully geared up and weighted down. It is mostly a great add addition if your weighted down or doing higher speeds on flat areas like the salt plains etc..

The increased damping is great for those who hit bump stops quite often when off-roading. A second shock would provide the additional dampening needed and also provide better control than a single shock setup.

Benefits

• Maximum vehicle dampening
• Reinforces the factory coil bucket and helps reduce flex
• Increased control at higher speeds

Struts

A strut combines the primary function of a shock absorber, it act’s as a dampener, with the ability to support sideways loads, not along its axis of compression. It is somewhat similar to a sliding pillar suspension. The most common form of a strut in an automobile is the MacPherson strut.

The MacPherson strut combines a shock absorber and a spring in a single unit, by means of which each wheel is attached to the car body. While struts sound similar to shocks there is a major difference between shocks and struts. That is that a strut is a structural part of the vehicles suspension system where a shock is not. A strut is also a crucial part of the vehicles steering system and greatly affects alignment angles.

Struts are most commonly an assembly of coil-over spring and a shock absorber. Other variants to using a coil-over spring as the compressible load bearer include support using pressurized nitrogen gas acting as the spring, and rigid support which provides neither longitudinal compression/extension nor damping.

Struts can fail most strut failure is gradual, not instantaneous but it is possible. The gradual failure becomes evident as a more trampoline like ride, your travel over bumps becomes worse, and you can have tire noise/ vibrations. This wear affects all of the strut components, the more worn out the shock absorbers become, the more worn out the spring will become, the more worn out the mount will become, and the more this will affect the shock absorbers.  So it can lead to pricey damages if not caught.

If your 4Runner nose dives when stopped suddenly, squats when rapidly accelerated, or tends to roll when going around curves on the roadway, These are all signs that your 4Runner will likely require strut replacement in the near future

Upper Control Arms

A control arm is a bar that has a pivot at both ends. Your 4Runner has a total of 4 two uppers and two lower also known as a double wishbone suspension system. In this section we are going to focus on the upper control arms and what control arm’s do.

Control arms are part of the suspension system. They attach suspension members to the chassis and manage the motion of the wheels so that it synchronizes with that of the body of your 4Runner. They are typically equipped with bushings on the frame side of the vehicle and a ball joint on the wheel side of the vehicle to the chassis and manage the motion of the wheels so that it synchronizes with that of the body of the car. They work with bushings, which are cylindrical linings that reduce friction and restrain the suspensions parts from going every which way.

The upper arm is shorter to induce negative camber as the suspension rises. The Upper control arms attach the wheel hub and steering knuckle, along with other suspension parts to the chassis of your 4Runner.  When the vehicle is in a turn, body roll results in positive camber gain on the lightly loaded inside wheel, while the heavily loaded outer wheel gains negative camber from the upper control arm.

Ball Joint

Ball joints are spherical bearings that connect the upper and lower control arms and connect to the steering knuckles. To explain how they work think of a human’s hip joint it works like a ball and socket, very similar to your 4Runners ball joints.

A ball joint consists of a bearing stud and a socket enclosed in a casing. Ball joints are made of steel and have a rubber boot to keep in grease. Usually, this rubber boot allows movement and expansion of the grease within. The bearing stud is tapered and threaded and fits into a tapered hole in the upper control arm and into the lower control arm as well.

Ball joints main purpose is to be the pivot between the wheels and the suspension of an automobile. Our 4Runners are a non-MacPherson strut automobile suspension, which means it uses two ball joints, the upper ball joint, and lower ball joint.  For those who don’t know what  MacPherson suspension is,  it is a suspension which utilizes one ball joint per side versus two, between the lower end of the strut and the lower control arm.

There is no exact lifespan that can be put on sealed ball joints, they can fail as early as 80,000 miles (130,000 km) in modern vehicles, and much sooner in older vehicles. They never fail without warning though.

Signs of a failing ball joint may start with a sudden burst sound as a result of ball joint dismantling. They will also begin to form a clicking, popping or snapping sound when the wheel is turned and eventually turn into a squeaking sound at the end of a stop when the gas pedal is used and/or also when hitting bumps. Another symptom could be a noise similar to a thud coming from your front suspension when going over any bump.

If you tear the rubber boot on a ball joint it can cause a dry ball joint. A dry ball joint like any other metal on metal part that is not properly greased/lubricated can have dramatically increased friction, In some cases, it can actually cause the steering to stick or be more difficult.

If a ball joint fails, the results can be dangerous as the wheel’s angle becomes unconstrained, causing loss of control. 4Runners are known for ball joint failure’s so they are something to make sure is in peak condition. In many cases they brake at the joint and either your passenger or driver side tire will come off and cause you to lose control and crash.

Ball joint UCA Cover Kit

Upper control arm ball joint covers are a tight fitting cap that protects the top of your balljoint in aftermarket control arms. It keeps dust, dirt, mud, and even water from getting down in there and causing rust and other issues. They are worth purchasing just to help with rust because an upper ball joint nut can be one of the hardest things to remove when it becomes rusted inside of your aftermarket control arm.

Lower Control Arms

A control arm is a bar that has a pivot at both ends. Your 4Runner has a total of 4 two uppers and two lower also known as a double wishbone suspension system. In this section we are going to focus on the lower control arms and what control arm’s do if you did not read the upper control arm section.

Control arms are part of the suspension system. They attach suspension members to the chassis and manage the motion of the wheels so that it synchronizes with that of the body of your 4Runner. They are typically equipped with bushings on the frame side of the vehicle and a ball joint on the wheel side of the vehicle to the chassis and manage the motion of the wheels so that it synchronizes with that of the body of the car. They work with bushings, which are cylindrical linings that reduce friction and restrain the suspensions parts from going every which way.

The lower control arms allow the suspension setting parts to rotate whenever the car is cornering-resulting in convenient driving pleasure. The lower control arm also synchronizes with the upper to keep all four tires to the motion of the vehicle to allow for a smooth and comfortable traveling experience.

Stock Lower Control Arms Replacement

While stock lower control arms provide plenty of strength and functionality there is always room for upgrades and there is always reasoning. Reasons to replace stock control arms would be, more strength, better bushing materials and typically a uniball in lieu of a ball joint. Which a uniball is a huge reason to upgrade due to our 4Runners along with Tacomas being known for lower ball joint failure.

Lower Control Arm Skids

While not everyone has Lower control arm skids on their 4Runners we must say they are a must-have for anyone who does heavy offroading. While a balljoint failure sucks it is not nearly as bad as tearing up or tearing off a lower control arm. A lower control arm skid provides extra protection to your lower control arms when offroading over anything that could damage them like rocks, stumps, and other obstacles in the terrain. So like your main skid plates to protect your 4Runners undercarriage lower control arm skids are a must have.

4Runner Lower Control Arm Cam Tab Gussets

Lower control arm gussets are meant to replace the weak factory alignment cam tabs. Th factory cam tabs can bend or shear off from a hard hit causing alignment issues. They are made of a stronger thicker material than stock so you won’t have to worry about them becoming damaged, unless you’re into rock crawling or other forms of offroading that have a lot of dangers. But in that case, these still will cause you to worry far less than running stock cam tabs.

Differential Drop Kit

The differential drop kit drops your differential down the drop height varies on the exact kit you purchase. The purpose of a differential drop kit though is to lower your cv axles back down to stock height or near stock height.

When running a suspension lift you raise your differential and cv axles which cause more tear on them. Differential drop kits are so worth it, they can be purchased cheaply and can save you from ruining your axles or even your front differential which could end up costing you thousands.

Body Mount Chop

The body mount chop is well known throughout all generations of 4Runners. It is done to the front body mount’s right behind the front tires. Why would you chop a body mount and alter it you might ask, well the reason to chop the mount is for tire clearance. Because you might have just purchased your new rims and tires and lift kit and got everything installed, but as soon as you go to drive your 4Runner you hear rubbing. Your body mounts near the front tires are commonly known for rubbing tire’s that are not stock. Luckily there are many kits available that provide new mount’s or side plates to replace the part of the mount you remove.

Limit Straps

What are limit straps? Limit straps are used when your suspension reaches full extension, something’s got to rein it in. If you don’t have limit straps, that something is your shocks and other parts you don’t want to be stressed. Add heavy axles, burly bead-locked wheels, and big tires to the mix and you’ve got a lot of force yanking downward on your shocks and other parts.

Even if you’re not going fast or getting air so to speak, your shocks and other parts still have to withstand a lot of force when the axles articulate over obstacles. So limit straps are a cheap solution to keep all of your expensive parts from being fully stressed when off-roading.

Benefits

• They are inexpensive
• They don’t interfere with operation of anti-roll bars on independent suspensions
• They are good limiters unlike, Anti-roll bars which are not good limiters when it comes to extreme offroading if you’re even using your sway bars, neither are shock bottoms or other parts that can be easily stressed like brake lines.
• CV joints are expensive
• CV boots won’t be torn as often
• Brake lines don’t stretch
• Bushings and ball joints don’t like to pivot to their limits
• How many times have you seen bump-stops set incorrectly or incongruent with lifted/extended parts? Straps (set properly) can protect you at full droop

Sway Bars

A Sway Bar also is known as (anti-roll bar, roll bar, anti-sway bar, sway bar, stabilizer bar) is a part of our 4Runners suspension that helps reduce the body roll of our 4Runner during high-speed cornering or over road irregularities. It connects opposite (left/right) wheels together through short lever arms linked together by a torsion spring. A sway bar increases the suspension’s roll stiffness, the stiffness is its resistance to roll in turns, independent of its spring rate in the vertical direction.

The purpose of a sway bar is to force each side of the vehicle to lower, or rise, to similar heights, to reduce the sideways tilting also known as the roll of the vehicle on curves, sharp corners, or large bumps. With the sway bar removed, a vehicle’s wheels can tilt away by much larger distances, which can be useful when off-roading your 4Runner but may not be a good idea for daily driving.

There are many variations in a sway bars design, one of the more common function’s is to force the opposite wheel’s shock absorber, spring or suspension rod to lower, or rise, to a similar level as the other wheel. In a fast turn, a vehicle tends to drop closer to the outer wheels, the sway bar then forces the opposite wheel to also get closer to the vehicle. So while removing sway bars are a good idea for off-roading due to providing more tilt distance at the wheels, trying to make any corners at higher speeds may bring your 4Runner onto two wheels or even cause an accident.

Benefits

• Better cornering
• Better stabilization of on-road use
• Disadvantages
• Less tilt in your wheels
• Doesn’t allow rear axle to move as freely

Long Travel Polyurethane Bushing Kits

Long travel polyurethane bushings are a great upgrade for those who are running a long travel suspension setup. Polyurethane bushings, in general, are an improvement vs the factory rubber bushings used all over our 4Runners suspension parts. The polyurethane bushings will last longer, stand up to road debris better than rubber, resist chemicals and oils, and handle compression and load better as well.

Benefits

• Last longer than rubber
• Looks better
• Chemical and oil resistant
• Handles road debris better
• Handles more load and compression than rubber

Sway Bar Relocation Blocks

Sway bar relocation blocks allow you to relocate your sway bars mounting points. This is useful if you’re running a lift or if you have done anything to cause your sway bar to hit on other suspension parts.

Upper Coil Bucket Tower Gussets

Upper coil bucket tower gussets similar to the lower control arm cam tab gussets replace the stock metal to provide a stronger mounting point. In this case, the mounting point is for your upper coil bucket tower. This is a good spot to replace with stronger gussets due to the factory coil buckets having a tendency to flex resulting in a bent or cracked upper shock mount tower.

Rear 4Runner Suspension Terminology

• Rear Shock/Absorbers
• Rear Coils/Springs
• HD (heavy-duty) Coils/Springs
• Extended Rear Brake Lines
• Lower and Upper-End links
• Rear Shin Guards
• U-Bolt Flip Kit
• 4Runner 3″ Rear Bump Stop Drop
• Rear Lower Link Guards
• Rear Adjustable Track Bar (Pan Hard Bar)

Rear Shock/Absorbers

The rear shocks are designed to reduce the effect of traveling over rough ground, leading to an overall improved ride quality and increased vehicle handling. While the shocks serve the purpose of limiting excessive suspension movement, their purpose is actually to damp spring oscillations. Shock absorbers use valving of oil and or gasses to absorb excess energy from the springs when in motion.

One design consideration, when choosing a shock absorber for your 4Runner, is where that energy will go. Typically in most shock absorbers, energy is converted to heat inside the viscous fluid. However, in hydraulic cylinders, the hydraulic fluid heats up. Then in air cylinders, the hot air is typically exhausted to the atmosphere. There are many other types of shock absorbers available though, such as electromagnetic types. The electromagnetic absorbers dissipated energy can be stored and used later. In general terms,  quality shock absorbers help cushion vehicles on uneven roads and provide a smoother ride.

The basic twin tube shock absorber consists of two nested cylindrical tubes, an inner tube that is called the “working tube” and finally an outer tube called the “reserve tube”. If your shock absorber is gas charged the overall design will be similar, the main difference will be a low-pressure charge of nitrogen gas is added to the reserve tube.

Next up we have the Position sensitive damping ‘PSD” for short, absorbers. It is another variation of the twin tube shock. A PSD shock absorber still consists of two nested tubes and still contains nitrogen gas. But a set of grooves has been added to the pressure tube, these grooves allow the piston to move relatively freely in the middle range of travel.

They also allow it to move with significantly less freedom in response to shifts to more irregular surfaces when upward and downward movement of the piston starts to occur with greater intensity. A PSD absorber is great for those who off-road because in simpler terms they are great on bumpy roads, the stiffening provides greater control over the movement of the vehicle.

Lastly, we have Acceleration sensitive damping “ASD” absorbers. ASD shock absorbers are able to sense and respond to not just situational changes from “bumpy” to “smooth” but to individual bumps in the road in a near instantaneous reaction. This was achieved through a change in the design of the compression valve. However, ASD shocks are only available from a limited number of manufacturers.

While there is a variety of different shock’s there are some Special Features offered depending on what you choose.

” Special Feature’s ”

• Some shock absorbers allow tuning of the ride via control of the valve by a manual adjustment provided at the shock absorber.
• On more expensive options the valves may be remotely adjustable, offering the driver control of the ride at will while the vehicle is operated.
• Additional control can be provided by dynamic valve control via computer in response to sensors, giving both a smooth ride and a firm suspension when needed, allowing ride height adjustment or even ride height control.
• Ride height control is especially desirable in highway vehicles intended for occasional rough road use, as a means of improving handling and reducing aerodynamic drag by lowering the vehicle when operating on improved high-speed roads.

Rear Coils/Springs

Springs are a vital suspension part they support the weight of your car and allow it to remain stable even in rough driving conditions. Springs/Coils expand when you hit dips on the road or when off-roading. They compress when you encounter bumps or cut into hard corners, They also will compress if your 4Runner is weighted down, especially in the rear.

A certain kind of spring, called air spring, can prevent the rear of your 4runner from lowering/sagging toward’s the ground. Air spring’s/Inserts determine ride height as well and can provide a smoother ride, they also, in turn, influence your overall steering and suspension.

The rear springs of your 4runner, unlike the front, do not have a shock absorber in them. Instead, they are mounted by themselves in the rear. Rear springs do tend to sag/lower over time due to regular wear and tear from constantly compressing and expanding while driving.

There are many spring kit’s available for your 4runner. They range from being designed for comfort and better stability to lifting your 4Runner, They do have rear coils that provide a stiffer ride as well for those who prefer it.

While 4Runners are not speed-demons, a stiffer ride is useful because as your speed increases a stiffer ride is needed to keep your 4Runners wheels in contact with the road. For off-roading you can get by with smooth riding lifted springs, While ground contact is important in most cases you will not be going fast while off-road.

HD (heavy-duty) Coils/Springs

Heavy duty coils/springs are just a beefed-up version of regular coils/springs. While there are different versions of heavy duty coils and springs they are typically designed to handle more wear and stress than regular/most aftermarket standard coils. They can also provide better resistance against more weight if you gear your 4Runner up. That can be a big plus for off-roading if you have a lot of gear and your existing coils allow sag which in return causes less clearance.

Extended Rear Brake Lines

Extended Rear Brake Lines are exactly what it says rear brake line’s that are longer than stock. Why are these needed/mentioned you might ask? Well even if your line reaches with a 3in suspension lift or any other lift stock lines just do not cut it for offroading. You have to consider axle sway and other variables. An extended rear brake line provides enough spare line to fully flex your rear end while offroading with any form of a lift.

Lower and Upper-End links

Sway bar links are the part that connects the outer ends of the sway bar to the suspension component. While stock links are good in most cases there is room for improvement.

One of the biggest benefits of replacing your upper-end links on your 4Runner is to correct the pinion angle for proper driveshaft angle, another added benefit as well is the increased flexibility of the axle as it articulations while off-roading for a more stable feel.

Most lower end links provide the same purpose as well but you can purchase them with a offset instead. By doing an offset notch the bushing is moved to sit higher on the link tube which in turn provides greater clearance between the axle housing and the link.

Rear Shin Guards

A rear shin guard prevents your rear shocks from dragging on rocks along with other obstacles you will come across during your offroading adventures. The shin guard is also designed to help prevent debris from wearing your shock’s shaft prematurely so that will help prolong the shocks life which is a huge plus for those who have pricier shocks.

U-Bolt Flip Kit

The U-bolt flip kit turns the U-bolts upside down so the bolt ends face upwards instead of facing the ground so they stay away from the rocks. The U-Bolt flip kit prevents both damages to U-bolt threads and increases ground clearance. It not damaging threads is a huge plus because removing a nut with damaged threads can be a hassle.

4Runner 3″ Rear Bump Stop Drop

The 3″  rear bump stop drop kit is designed to move your factory bump stop down and to the rear to properly re-align and correct for aftermarket lifts. It will also extend the bump stop to help keep larger tires from damaging your body and keep the shocks from bottoming out when under load off-roading.

Rear Lower Link Guards

One of the thinnest parts of our 4Runners frame is the lower link mount and is also the lowest hanging point making it the most vulnerable to being hit by rocks.  The frame at this part is less than 1/8″ thick and is very susceptible to bending and eventually cracking which can cause major issues. Rear lower link guards add in extra material that warps completely around the frame mount, providing the ultimate protection against denting and cracking.

Rear Adjustable Track Bar (Pan Hard Bar)

An adjustable rear pan hard bar adjusts for your lift height and returns your rear axle/vehicle to tracking straight.