Front Live Axle Suspension Info



There are many options available when it comes to modifying the front live axle suspension and steering. Early trucks use a leaf spring front suspension with the shackle in the rear. Steering is push-pull variety and a torque rod is used to control axle roll during hard braking. Here I'll discuss some of the various front suspension issues.

Clicking on any category will take you right to that particular section.

  • Torque Rod
  • Moving the Axle Forward
  • Shackles
  • Shocks
  • Driveshafts
  • Dropped Front Mounts
  • The Weak Frame Spot
  • IFS to Live Axle Swaps

  • LIFT CHOICE

    The questions always arise......how much lift do I need to clear some size tire....and......which lift is best. First, one needs to decide the type of 4WD application for which the truck will be used. For example, mud trucks typically require stiffer springs than do rock-crawling trucks. Based on these considerations and desired tire size, type and height of lift can be determined.

    In general, lifts of up to three inches can be done by simply replacing the front spring packs. Lifts in the 4-6 inch range usually require longer or relocated brake lines, perch shims to correct caster, driveshaft mods, and a dropped draglink or flipped ball steering arm. Some people may install lifts without changing these items, but most, if not all, are needed to retain safety and maintain good suspension travel.

    I cannot speak much about mud running setups, but have a good bit of experience with rock-crawling setups. Most aftermarket spring kits use stiff springs that do not flex well when large amounts of travel are sought. My experience has shown that thinner leaves (~.280" or less) seem to work best for spring packs if maximum flex and travel is the main goal.

    Thinner leaf packs such as these will typically allow the pack to flex backwards, allowing lots of travel. Realize, though, that allowing the springs to flex backwards may shorten their life. I have not found this to be a problem with seasoned springs I have used (more on this below).

    From opinions I have heard, it seems that Old Man Emu (2.5" lift) and Alcan custom springs seem to be the best liked among those made on the market. Both offer high quality springs with nice, flexy leaf packs. Note that these are typically on the upper end of the price scale as well. One advantage to using the Alcans is that they can be custom ordered in any lift and length with the center pin hole relocated if needed (more on this below).



    FRONT HYBRID SPRINGS

    In the past I have run lift spring packs from several different manufacturers. However, I always found that aftermarket 3-4 inch lift springs were typically too stiff, would not bend backwards well, and often sagged and lost some lift after a year or so. As such, I went in search of other solutions to provide the lift I needed and the flex I wanted for rock-crawling.

    I switched to some homebrew hybrid front springs several years ago. These are five leaf packs I made up using a Datsun 2WD main leaf (0.280" thick), and various Downey and Mazda leaves I assembled to my liking. The pack has minimal arch to it and flexes very well. I can easily push the springs to the bumpstops under articulation. The only thing I found I did not like about this setup is the fact that I lost about an inch of lift compared to the very stiff 3 1/2" NWOR springs I had been running. I will explain how I fixed this below.

    I have talked to Toy owners who have tried other spring combinations. One possibility is using Jeep Wrangler springs. These are slightly wider (2.5") compared to a standard 2 3/8" wide Toy spring. However, I have heard the Wrangler springs can still be squeezed into the front mounts. These packs use thin leaves and are fairly flat but alone only yield about 1 1/2 to 2 inches of lift.

    Stock Toy front springs are about 45.5 inches long across the arc. Wranglers are just slightly longer, and the Datsun main leaf I am using is still longer at about 47 inches. Others have also used stock Toy or aftermarket lift rear main leaves on the front and built packs from there. These mains are longer than stock and provide a good shackle angle for the front spring packs.



    DRAGLINK ISSUES

    Live axle Toyotas use a push-pull steering system. A draglink is used to connect the pitman arm from the steering box to the knuckle arm at the front axle. The stock draglink rests at a near horizontal angle and is not adjustable in length. Whenever lift is added to a live axle truck, the angle of the draglink rises, the same as for the torque rod. For lifts up to about 3 inches, this is not a problem as the original turning radius can be maintained.

    However, when suspension lift exceeds 3 inches, the stock draglink is no longer long enough to provide full lock-to-lock turning capability. Left-hand turn radius is not affected, but right-hand turn radius is increased because the draglink is not long enough to push the knuckle arm to full travel.

    When very tall lifts are added, the draglink can become tilted at such a steep angle that the lower end may come in contact with one of the leaf spring u-bolts. Also, another effect of adding the lift is that the steering wheel is pushed out of alignment. This problem can usually be corrected by removing the steering wheel and repositioning it so that it is aligned straight when the tires are directed straight ahead. The only way to restore the original turning radius is to install a longer draglink.

    Aftermarket companies sell adjustable dropped draglinks to replace the original. These replacements can be adjusted to fit a specific lift height and also offer a 3 or 4 inch drop to allow full component clearance as in the stock configuration. It is necessary for the pitman to travel further on a lifted truck to gain the same knuckle arm movement. Luckily, Toyota steering boxes have the extra travel needed for reasonable lift heights.

    When lift is added such that the draglink is no longer parallel to the ground, the steering geometry of the truck is altered and you may find that the truck may wander somewhat on uneven roads. This is not severe for moderate lifts. However, there are companies that claim that their adjustable draglink will remedy this problem and restore the steering to the stock geometry. This is absolutely not true. An adjustable dropped draglink will solve the turning radius problem, but will not do anything to correct the steering geometry problem just described.



    KNUCKLE ARM

    When lift heights approach 6 to 8 inches, it is also necessary to install an aftermarket knuckle (or steering) arm. This is a knuckle arm that is extended upward, or has the ball flipped to the top of the arm to help restore some of the geometry loss of the steering system.

    In the cases of both knuckle arm and draglink, there have been instances of people heating and bending the stock components, or adding length to them. While this may seem like an easy and cheap solution, the strength and safety concerns are serious, and it is best to purchase a tested and proven aftermarket unit. Loss of steering at the wrong moment would be most unpleasant. See the following section for info on steering arm weaknesses.



    CROSSOVER STEERING

    When the stock steering system is used with a long travel front suspension and/or used for hard core wheeling, there is a risk that the driver side knuckle steering arm will eventually break due to long term stress. Most often, the arm breaks like the one shown in this picture. Other times, though more rare, the arm will fracture through the bolt holes where the arm bolts to the top of the knuckle.

    Even when running a dropped draglink there is a significant risk in breaking this arm. Simply put, as the front driver side suspension drops, the draglink puts a pulling and twisting stress on the steering arm. Over time, the arm fatigues and will eventually break. Those running off-the-shelf 3 or 4 inch lifts may never experience a break. However, those that have tweaked their front end for lots of travel are at risk of this arm breaking.

    One way to fully eliminate the risk of this steering arm is to swap over to crossover steering. This generally involves swapping to a cross-pull type steering box such as the one found on IFS trucks. Like the original steering setup, a tie rod is used. However, a new draglink is added to connect the steering box to a steering arm on the passenger side knuckle. This eliminates the drawbacks of the push-pull steering system and provides a system capable of operating over a much greater range of suspension travel.

    Owners have fabricated various forms of crossover systems using modified steering arms and fabricated arms. All Pro Off Road offers crossover steering conversion kits that come complete and ready to install. All Pro's web page also explains the ins and outs of crossover steering in more detail.



    TORQUE ROD

    The front live axle torque rod helps prevent axle roll under braking and 4WD acceleration. However, it can also limit front suspension travel and articulation in cases where the front springs have been modified, or longer or softer springs are used. Also, as lift is increased over about 3 inches (or the axle is moved forward), it becomes necessary to adjust the length of the torque rod so that it is not under any load with the suspension at rest.

    If you lift your truck over about 3 inches or use longer springs that allow more travel, you may have torque rod problems if you do hard core rock-crawling where you articulate the axle to extremes. Leaving the torque rod in place puts you at risk of tearing the mount at the frame or breaking the tower on the axle. I have seen both occur.

    On the other hand, removing the torque rod also has its risks. First, you have to be careful that your driver knuckle steering arm and draglink are not put into bind. In such a case, you risk breaking the steering arm. Second, fourwheeling without the torque rod will allow the axle to roll somewhat. The softer the springs, the more the roll. This may cause the pinion angle to roll enough to bind the u-joints in the driveshaft or cause the driveshaft slip joint to separate, depending on how much driveshaft travel you have. Opened leaf spring clamps will also exaggerate axle roll and may cause problems when the torque rod is removed.


    One other point.......the stock draglink and torque rod are designed to travel in like arcs so that neither one binds throughout the full range of travel. As such, bumpsteer at stock height, and for reasonable lifts, is minimal with this design. Some people have attempted to solve the problem of the torque rod limiting spring travel by relocating the torque rod frame mount. Typically they move it forward to the front crossmember. The problem in doing this is that now the draglink and torque rod no longer travel in similar arcs. Increased bumpsteer is usually the result of this type of modification.

    Here is some additional explanation of the torque rod function by James Stevenson.......

    The Torque arm controls the bumpsteer in the OEM draglink type steering. Bumpsteer is created by the movement of the axle forward and back. The reason for this is simple. As the spring contracts, the length between the spring eye gets larger. As one end of the spring is fixed (fixed eye) this causes the shackle to move back. Along with this the axle is moved backwards by the same amount as the shackle.

    As the draglink is a fixed length, bump steer is created, by the movement in the axle. Or to put it another way, as the axle moves up it moves backwards. This means the steering turns right as the axle moves away. The torque rod stops this by bending the spring so that the axle stays in the same position relative to the draglink. As the axle moves back the torque rod tower causes the axle to rotate. This rolls the steering arm forward so as to keep the distance from the pitman arm to the steering arm constant.

    What this is doing to the spring is bending it. The portion in front of the axle will create more arch , that's ok. However the section of the spring between the axle and shackle will bend in an S. This is why the drivers side spring loses its arch so quickly. Its also the reason why broken front leafs are usually on the drivers side half way from the axle to the shackle.

    With all that explained its easy to see why the torque rod restricts travel. That's it job really. If you disconnect the torque rod you will be placing a lot more stress on the steering arm. With the torque arm removed, as the axle moves the steering changes (bump steer) will be transmitted into the steering arm. This is forcing the wheels to turn. This in itself is not a problem except when talking shock loads. Big bumps in the road produce sharp powerful changes in the loads on the arm.

    This eventually causes the steering arm to develop stress cracks and break. In terms of rock crawling this is not really an issue as the stresses are minor. However the arm will still break just not nearly as quick as a rig used on high speed dirt roads. The steering arm is far too important to risk breakage. If it goes on the highway at speed you will have a devastating accident and possibly kill yourself and others. If you remove the torque rod and drive the vehicle on the road the only safe answer is a crossover conversion.


    In this article I detail how to make a quick-release torque rod. Please note the risk of removing your torque rod as well.



    MOVING THE AXLE FORWARD

    Moving the front axle forward can help gain greater tire clearance at the rear edge of the front fenderwell. This can be done in several ways. First, the axle perches can be redrilled to gain an inch or more relocation. (Brian Gallus reports he was able to get 1.5" by enlarging the rear hole on the drivers side and duplicating the hole on the passenger side.) Second, leaf spring main leaves can be redrilled (questionable, safety-wise). Third, different main leaves can be used that locate the pack center pin further forward.

    One possible option is the use of stock rear main leaves up front. This will relocate the axle forward about 2 inches. However, due to the longer spring length (about 47 inches, 20.5 inches center to forward eye) the shackle may lay at too shallow an angle. This may work with a longer shackle with the stock mounts, though I have not confirmed.



    SHACKLES

    As a general rule, shackle angle of about 45 degrees is optimal for best overall travel. Longer shackles can be used up front to gain lift. Experience has shown that 2 inches over stock is about the maximum length that can be used without risking kinking the front springs or causing other geometry problems. As with many suspension modifications, caster must be checked and possibly corrected when changing shackle length. Shackles serve to control spring movement and can also affect the effective spring rate of the leaf springs. If the shackles are set too vertical, they can limit downward spring travel and provide a harsher suspension ride. If your shackles began to lean too far rearward, they can hit the frame under compression. One possible solution is use of the "Wide-Body" greasable front shackles fabricated by Frontier 4WD.



    SHOCKS

    There are all kinds of front shocks that can be used on a live axle Toyota. The most popular seem to be Rancho RS9000 shocks. The big advantage of the Ranchos is that they have five dampening adjustment settings so that you can tune the shock to your springs, or raise the rate when hauling camping gear and such. However, I have heard from people who claim the Ranchos do not hold up well for high speed driving. Evidently they heat up quickly and fade.

    Depending on your lift and travel you can choose a shock size that works best for your setup.

    I have found that to maximize the front suspension travel, it is necessary to relocate the top mount higher and run a longer shock. The shock most often used is the Rancho RS9012. This shock was made for a dual shock application and is valved lighter than most shocks. However, the range of settings is plenty wide to accommodate any Toyota application. The shock length is about 19 inches compressed and 33 inches extended, eye to eye, for about 14 inches of travel.

    There are several ways to extend the top mount. The original method (which I still run on my truck) is to cut the top 2-3 inches off the stock mount and weld a Ford F-250 shock mount onto the original mount as shown here. Due to the long shock length, it was necessary to trim a hole in each fenderwell and locate the top of the shock inside the engine compartment.



    There are a number of styles of these Ford mounts and I am not sure which particular year model these came from. I know both stud and eye mount varieties were used. I happened to use the stud type and cross drilled them for my shocks.

    From the aftermarket, All Pro Off Road offers their good looking weld-on shock hoops to run 9012s. These are trail proven units.



    DRIVESHAFTS

    The stock driveshaft is a CV style unit. The early live axle versions have good angular movement at the CV. However, some or all of the IFS units have poor angle limits and will bind when used on a live front axle. Since the Toyota truck and 4Runner front driveshaft is fairly short, longer travel front suspensions will most likely cause the relative short stock splines to separate under extreme front axle droop.

    Adding a Marlin dual case can go a long way to solving the excessive spline travel and the fairly extreme angle the front driveshaft must traverse when there is a lot of travel at the front end. The CV joint may also be replaced with a standard yoke to gain more angular travel. Best to just check this closely once your suspension is complete and decide at that point what will work best for you.

    For really long spline travel, places such as Gloeco in Phoenix can build long spline driveshafts with 6-19 inches of spline travel. With that setup, size it a tad short and you can continue to tweak your front suspension and not need to rework the driveshaft again.

    If you must use a standard or short spline driveshaft, you can put a limiting strap on the front passenger shock to limit droop at that corner. Just note that the straps do stretch some under load and account for that accordingly. Also, if you run soft front springs, the axle can roll under torque. Not only will the axle drop, but the pinion can turn downward under load, possibly separating the driveshaft.



    DROPPED FRONT MOUNTS

    In order to address the height loss due to the flatter springs, I decided to increase lift up front by dropping my front spring mounts. This would provide no real increase in approach angle or clearance but would give me front end lift and allow me to keep the flatter springs. Since my front springs are also about 1 1/2" longer than most Toyota springs I wanted to move the front mount forward slightly as well.

    I built a front crossmember from 2 1/2" x .125" wall box tube so that my overall spring bolt drop was about 2 1/4" and the bolt was moved forward about 1 1/4". I also provided a spring bolt hole in the stock location in case I ever wanted to used standard Toyota lift springs again. For more versatility, I made the front hangers capable of accepting either 2 3/8" wide Toyota or 2 1/2" domestic springs. For Toyota springs, I just add a 1/8" thick large flat washer inside the hanger. The stock front hangers were cut off flush with the front crossmember. The new crossmember was bolted and welded to the original crossmember and to the frame rails.

    This photo shows a front view of my added crossmember. It is not yet welded on in these photos, but is bolted on using tabs on the crossmember and two of the existing tapped holes on the stock front crossmember.


    This angled view shows the spring hangers with the two hole locations.


    For added rigidity I added an angled support at the rear, on each end. This support is welded to the added crossmember, and bolted into existing holes under the frame rails. Here the mount is bolted in place with some temporary bolts.


    You can see another set of dropped front mounts that David Moore used on his truck. These pictures show his mount design.



    THE WEAK FRAME SPOT

    I have seen a trend such that live axle Toy trucks that are wheeled hard and/or have heavier engines installed in them may develop a frame crack just behind the driver side forward spring mount. This occurs on the back side of the spring mount where it meets the frame rail. It seems that steering and suspension stresses may cause a crack to form here. When the problem occurred on my truck, I was hesitant to rush in and weld the crack as I was afraid it would continue to fracture or simply redirect the problem to another area.

    I watched the crack over a period of several months and it continued to grow slowly. In an attempt to stop the crack growth, I made the bracket shown here to reinforce the area. It bolts in three places to provide more rigidity here. Location 1 is a factory threaded hole in the front crossmember. Location 2 is one of the tow hook holes. Location 3 is the spring pack bolt. This bracket stopped the growth of the crack successfully for more than a year. I then changed over to my dropped front mounts and the crack was no longer an issue for me.




    IFS TO LIVE AXLE SWAPS

    A swap gaining in popularity is that of converting from IFS to a front live axle. There are several excellent web sources for completing this swap.


    Chris Geiger had All Pro Off Road perform a live axle swap on his 2nd generation 4Runner.

    David Moore recently completed a live axle swap on his 3rd generation truck.

    Jack Alford was probably the first to document a live axle swap that he completed on his '86 truck.

    Thanks for reading!


    Copyright (c) 1998, 1999 by Jay Kopycinski, All Rights Reserved.