Outer Limits 4x4 Board

G'day guys,

I thought I'd do a separate write up for the suspension mods that I'm doing on the rear of my build. I'm extending the wheel base of my shorty as well as triangulating the upper links. Although this is being done on my patrol shorty chassis, the basic process can be used on pretty much any vehicle including doing a coil spring conversion from leaf.

Now a bit of a disclaimer. I am not an engineer although these mods are being engineered and I am following their advice for how this is done. I also haven't done any welding for about 4 years so I'm a little rusty on that at the moment.

This is also the first time that I've messed around with the geometry of the suspension to this extent so if I'm missing something then feel free to add to this thread.

First thing I did was to take the cab off the chassis. This isn't something that is essential but it makes it soooooooo much easier. The alternative is to just lift the cab up to give you enough room to move. You need to remover a few things as well from the chassis like the shocks, springs and fuel tank. You'll also need to remover the fuel and break lines from the inside of the chassis so you don't damage them.



Next thing is to crack out the grinder and start cutting all the bits that you don't want or that need to be moved.

I am moving the rear diff back 300mm so I had to remover the shock mounting cross bar as this is where the springs now sit. I also cut the spring towers off the chassis but using a cutting disc and cutting the mounts just inside each of the welds so I could re-use the mounts. I also did this to the panhard mount as well which I'm selling with the rear diff for a coil conversion that a mate is going to do. I've also cut the bracing from each side of the cross member that has the upper control arm mounts because I'm moving these mounts as far out to the side as I can so I can triangulate the upper links.

Next I made a cardboard template to the shape that I needed to build up the chassis rails because it drops down just behing the original mounting point. Then I welded the original spring mounts to the modified section of chassis.


This is all I have done so far. I'll take a lot more pics as I go and finish this thread.

Yeah. The CofG I wasn't too sure of so I was guessing on that. I was figuring that the engine will sit around where the top of the wheels will be. I'm not lifting it too much. Only 3 or 4 inches. But a 2 inch body lift as well. So its still a bit of guess work. I don't mind having higher anti squat though. It does help to launch at a climb but not always a good thing for a shorter wheel base. haha. Here are the revised calcs.

Ok so after tacking it all together and double checking all my measurements and making sure that everything would work the way I want it to. I went ahead and boxed it all in and welded it all up properly...... Well as properly as my skills allow.

good of you to post progress pics. its nice to watch something coming together.
I would make some new lower shock mounts while youre at it if I were you, mine started bending after some little dents from rocks the passengers side one started twisting itself toward the wheels.
note the mud, it hides my welding which is worse than yours.

also dont forget to weld some brake line mounts on, I forgot and finished up with cable ties and bits of hose which looks terrible.

Already planning on the shock mounts. I was thinking that I need to move them because they are not even on the diff but I'm still trying to figure out exactly why they are offset to the diff. They are closer to the left than the right. My only thoughts are that they are that way because of the panhard mounting on that side of the diff and also the way the torque from the drive shaft reacts with the diff. If it is because of torque then I'll leave them in the same spots but with better mounts.
I still have the original break line bracket that I cut off so I can just weld it back on. I'm thinking of an in cab brake bias lever though instead of mounting that stupid spring to the axle again.

As for my welding..... Well it might be a little better if I had a decent welder with a duty cycle longer than 20 seconds. At least its stopping me for doing long runs that might bend the housing. Just trying to show that I'm not just a web wheeler. I can fark things up on my rig just a well as anyone.

quite an un-researched guess but is the shock thats mounted closer towards the wheel the one that has the exhaust next to it? It couldnt be as simple as spacing to clear the exhaust could it??

great threads by the way.

passengers side is inboard as far as possible against the panhard mount on the diff.
drivers side is outboard as far as possible without getting smashed by the chassis side panhard mount at full compression.
end result = drivers side shock is 25-30mm further inboard than the passengers.

I ran the thing up and down on the hoist all day with no springs in trying all different positions for the brackets to get it as good as possible.
I wanted to put them straight up and down, but they would finish up too far inboard so I had to lay them inward.
because of the lean I finished up with exactly 10 inches of travel with 12 inch shocks.

the brackets are so long because the shocks are a very large body with external bypass tubes. one lower mount just touches the panhard if you look closely you can see the rub marks, I have since ground part of that nut away.

Well my daughter isn't at my place so I can get some more done to this build. I've started doing the chassis mounts. Just need to drill them out and then make the control arms and bolt it back together. Then just fab up the cross bar for the shock mounts, bump stops and get a longer tail shaft then its all done. Then on to the rest of the build.

Well both chassis mounts are now done. I have done a final measurement on the trailing arm lengths and I need 730mm uppers and 980mm lowers.