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