Ute wags it's tail over bumps

[surrender]

Gday everyone,

Got a quick question that I cannot figure out myself. I have a 1990 GQ ute, big lift with no sway bars and a rear 4 link. I do understand that a sway bar will stop the body roll but this feels like a different issue. When I hit any sort of bump in the road, be it a pothole or even just a crease in the concrete, the back of the truck wobbles around like you are sitting on jelly, slightly side to side and sometimes bad enough that I need to correct the steering.

A mate driving behind me also noticed it one day so it must be a decent wobble, it's basically like the car is wagging it's tail while bouncing around. I am not a mechanic and thought there would be somebody here that could help me out. Am thinking I should replace all the bushings in the 4 link and see if it stiffens up, I know a sway bar would help, but my issue is not with body roll while cornering, but with this weird jelly rear end whenever I hit a bump. Anybody with any ideas or experience with something like this?

Cheers, Sam.

[Dominator]

You could try replacing the bushes in your arms but it is also a possibility that the 4 link is not set up correctly and your getting lateral movement as a 4 link does not have a panhard to limit side to side movement and relies on the correct geometry.

[surrender]

Yeah that thought came to mind also, the bushes in the arms do look pretty flogged though, I am hoping that is where the lateral play is coming from otherwise it sounds like it could get expensive fast. I think I will stick to my plan of all new bushes and then take it from there, won't hurt replacing them all anyway. Cheers Dominator

[growler2058]

Dunno a lot about a four link but can a pan hard be added? Big gutsy lump of steel should stop anything!

[surrender]

I think I would still be able to run a panhard? Although am not completely sure. The 4 link is triangulated so that should pretty much rule out lateral movement in the first place, I am hoping that the play is really only due to needing new bushings.

[Dominator]

You can add a panhard to a 4 link but it kinda defeats the purpose of changing from a 5 link as thats is what the triangulation is for. If the bushes look worn then definitely replace them and fingers crossed it sorts it for you.

[macca]

Does this happen with a load? I have ajustable shockies on the rear, been told by supplier if the back is skittish they are set too firm and need to be softened. You may have a suspension set up that is not compliant enough for the conditions you describe.

[threedogs]

I would have said shockers too, but change the bushes and see how that goes,
Do I fix at a time then you'll know what it was, rather than do 2 things and
not know which fixed it.

[surrender]

Have not driven the car loaded up yet, did not think about shocks but I think I didn't think they would be the cause due to the movement being side to side and floaty rather than firm and skittish. The front always stays tracking straight when this happens also, but the back floats around just like a dog wagging it's tail. Very odd feeling

[Ben-e-boy]

I think its a set up issue. What angle are your upper arms at the diff. A 4 link (from memory) is set to a minimum 40 degrees. I have heard of people setting them to 60 degrees to get rid of the panhard. I dont know how well it handles at speed as I havnt driven with a 4 link. Basically you have bought an outlaw class comp truck which isnt designed for road use.
secondly, its too high which will not help your cause.
thirdly, It is going to take alot of money to get it to a point that is suitable for your need. ie work,daily,touring and weekend play as stated in your build thread. Again you have bought something built for outlaw class compitition. not really anything else

[surrender]

It handles like shit at speed, the lateral movement in the rear end nearly steers the car when you hit a decent bump. It is definitely a set up issue, I got under the car today and came to the conclusion that the bushes are shot, so they will be replaced with new ones or if I am going to spend the money, I will see what I can do with some urethane bushes and some roller bearings to hopefully completely remove any play regardless of running a panhard. I think the trouble is because the shitty bushes aren't design to accomodate the lateral force and they are just getting crushed.

I didn't buy the truck as it is to do my touring and work duties, probably won't be an easy process getting it to where I want but I see no issue in a project. I also realise it is too high, but with it surrounded by barwork I can't get the body lift out unless I cut half the cage off and modify the front bar and sliders. Will be taking to it (albeit unfortunately) with an angle grinder tomorrow to get started on these issues. I would prefer to be running a 3" lift all round with 37's as my COG at the moment is doing me no favours with this 4 link issue, but I'm not, and I'm also about to buy tyres so I won't be buying new springs any time soon. It'll get there step by step, comp truck with the camping gear on the back? Far fetched but far from impossible.

[surrender]

Also tossing up the idea of incorporating heim joints into the 4 link but not sure if it has been done or if it's even a viable option.

[Dominator]

Heim joints are used in 4 links all the time but that is on rock crawlers etc. don't know how they would handle at speed. I think your best to try some nolothane bushes in the arms and see if that stiffens it up a bit. While nolothane are not ideal on a 4wd they are probably a worthy compromise for your situation.

[surrender]

Ah ok that makes sense, I think I may have seen them used on a trophy truck 4 link once but knowing the money that goes into those trucks it could have many other components working in favour of it. Will look into nolothane bushes also, just about to take the truck down to the local 4wd shop to get a second opinion. Cheers fellas, if you have any more info for me it's much appreciated.

[surrender]

Just left the truck at the 4wd shop down the road, the dudes down there are bloody excellent and not only helping me out but also genuine blokes who love their 4bys, tail shaft is getting replaced because that one was dented to pieces and throwing everything out of whack, they even think it is contributing to the movement in the rear end, I knew it needed replacing regardless but did not know it could be the cause of some of the shake. The shocks are also being relocated again, this time to the front of the diff and also spaced farther apart to counteract the body roll and to allow for a panhard to be put back in to eliminate the waggy tail.