Rear Upper Boomerang bushes - stuffed?

[glend]

Here's a question for Cmohr and anyone else that has pulled out the rear upper control arm (aka boomerang):

For some time now I have had driveline movement (fore and aft) when accelerating from a stop or comng to a stop, as if something was moving around. I did put up a post on this some months ago describing it as a thunk. Recently I rebuilt the front end and checked all the bushes not changed and so I know that is not the cause. Talking to another local KJ CRD owner we sort of narrowed the problem down to the rear bushes, and most likely the uppers. Since there is no 'steering effect' there was probably nothing wrong with the lower control arm bushes. An inpection today with a good torch and a mirror shows that the lower control arm bushes look good - no distortion or collapse or cracking (as expected as they are not subjected to any twisting effect due to the lift). The upper control arm bushes tell a different story. Because of the axle being pushed downward by the lift the bolts holding the upper control arm to the body are at an angle to the mounting hole - thus putting stress on the bushes and distorting them fairly significantly. I have cracks in the bushes on both sides of the rear upper control arm (looking from below). I suspect this is the cause of the rear axle movement. The ball joint where the upper control arm attaches to the diff (surprisingly) looks ok. These bushes are nearly four years old and with a 3" lift in the rear there was always going to be stress on them.

So I know Cmhor has changed these upper control arm bushes (in B1 right), and the Service Manual removal section seems straight forward, so are there any tricks to the removal?

Is there a fix for this long term or will I be forced to do this again and again over the years? or put up with the movement?

I have attached some photos but without a macro lense and a smaller camera to get into the spaces there - these are the best I can do. They certainly show the running angle and how the bolts would push the bushes out of shape over time. The first photo is probably the most useful in seeing the angle distortion.

As far as a fix is concerned, there are a few options: a new boomerang from JBA (which comes with the bushes and balljoint already installed (the shipping quote doesn't look any worse than the Front A Arms):



http://jeepinbyal.com/prod-Control_A...Upper-769.aspx

and then I would rebush the old one to be ready to go in when it has to be done again.

JBA wants $157 and Morris 4x4 has the same thing for the same price. I know your saying that's nuts because the bushes would only cost $15 each from Morris, plus the cost of the ball joint, but there is also the time required to remove the thing, take it to Pedders to rebush the thing and reinstall it:

http://www.jeep4x4center.com/product...umber=52088425


It would be nice if there was an aftermarket boomerang with bushing angle correction but JBA's 4link is just too expensive for me but it looks so nice. Hmmm Heim Joints!



http://jeepinbyal.com/prod-KJ_Tri_An..._Link-735.aspx

Finally, this looks promising, there is a bracket available that bolts on top of the diff to extend the rear boomerang drop, could this not also be used to correct the boomerang running angle and save the bushes? It's a cheap solution, here it is:



http://jeepinbyal.com/prod-Link_Extension-463.aspx

I'm thinking of just ordering the extension bracket and the bushes and this should both fix the problem and keep it from coming back.

This is not an advertisement for JBA, just find me someone else that has all this stuff for the KJ.

Postscript: I have emailed Marlin at JBA to ask if they can make me a 3" Extension Link, or whether a 4" would be ok with a 3" lift without any chance of body impact of the arm.

Opinions and suggestions?

[Dirt Pig]

The Link extension and new bushes would be the cheapest fix.
That's the way I'd go.

But you'd still have to do the labour and you need a press to drive the bushes in/out

The Triangulated 4 link looks the part But I wouldn't buy it; even if I was flash for cash. I was put off by the idea of welding it to your diff.

[CHEQUER-PLATE CHICK]

Great Information. Thanks Glend.

[glend]

I just had an email back from JBA (Marlin) and this is what he said about the Link Extension:

"You need the 4” link, it is 2.5 inches of set. So your 3” lift will be fine.
The material is ½” steel."

I think I will try it out, it doesn't cost that much ($52) and if needed I can reinforce it with my welder.

Update: Bushes and Link Extension have been ordered.

[cmohr]

Good morning Gentlemen, and Ladies watching. first, yes. Two, on a dog only.

Three, This has been a problem with these tri link rear ends, even the Grand cherros have experienced the problem. Those body to trilink arms are of cousre under a fair bit of stress with the increased static running angle achieved when a lift is installed. I have had many disscusions on Lost and here about the problem. As Glen states, Yes I had a thump in the rear end, and it ended up being the rear ball joint itself, the bushes where actually not that bad, but, I could clearly see movement in the ball joint and it was that causing the noise. When the rear end is extended downwards the running angle for the ball joint is similar to what happens in the upper control arms in the front end, at there most extended point, they are stressed to there most articulated point. So when this happens in the rear ball joint, what happens is the rubber it is mounted in is ripped, and the top of the ball joint is able to knock on the inner capping of the press fit outer casing that pushes into the upper tri-link. Al's extender, does, raise up the mounting point for the rear end to the tri-link arm, so does to and extent relieve some stress on the ball joint, but not all. It will mean the tri-link will be returned to a more level angle, (more like the standard running angle of the arm) so a great relief of stress on those body to tri-link arm. What it does not address is the angle of the rear diff itself, as the length of the upper arm is not changed, so the pinion angle will not be changed from standard. As a general rule, with most other 4x4's , you see that the pinion angle is one of the more common things most change out the standard control arms to rectify. What is needed, is a longer upper control arm, to tilt the diff upwards at the front, so as the rear uni is running more in parrellel with the rear drive shaft, reducing stress on that uni, and drive shaft vibrations.

So, Yes, the Al's extention, will relieve stress on the upper tri-link to body mounts, Yes, i will lessen, the stresses on the upper ball joint, but it will not correct diff pinion angle, or the position of the rear wheels in the wheel wells. I myself have often thought of getting the extension myself, but, just have not got around to it.


Removal of the upper arm can be tricky, First make sure the rear of the car is safely supported on jacks, I leave the car still sitting on its wheels, and some weight still on the suspension itself. You need a jack under the front end of the diff, so as it does not drop downward when removing the upper arm. Undo the body to upper arm bolts, then undo and remove the retaining bolt that holds the ball joint to the diff. Now it will be hard to get the ball joint out of that joint. I use a second jack with a length of wood up to the control arm (puttong upward pessure right beside the ball joint) and jack up the upper control arm til it comes out. The arm then simply drops out. You've most likely then seen my post on pressing out the bushes and the ball joint, replacing is done in reverse order, place the arm back up in postion, put the bolts in at the body to control arm mounts, Just dont tighten them (reason is that when the arm is even at a slight downward angle, you won't get the bolts in), then line up the ball joint, then.......... jack up the front pinion end of the diff, till you can pull the ball joint down into the mount. Replace the bolt and tighten all the bolts up.

I have thought many times about adjustable rear control arms. For lower arms, those from a TJ will fit, but there seems nothing for the upper. Als, big arse 4 point Tri-link, is complete overkill in my opinion, plus, not easy to fit, major welding, engineering require, plus, in Australia, rose joints on a street vehicle are illegal, so rules out the whole thing. A replacement upper arm should not really be hard, There are pics on Lost of some guys that have made adjustable upper arms. Then, there is ironrock, who make an adjustable upper arm for the WJ. I think it could be easily modified for the KJ.



Bit of jib a jabba here... http://www.lostjeeps.com/forum/phpBB...hilit=tri+link

[glend]

Wow, thanks cmohr. Yeah, I agree there are options that are just not legal here. For now I am happy to replace the bushes and ball joint and put on the Link Extension to protect the upper arm mounting components. It remains to be seen how this Link Extension will stand up to outback corrugations, I believe there was at least one guy in the US that managed to break one (swampguy I think). Which is why I want to have a good look at reinforcing it before I put it in.

Is the pinion angle as much of a concern if your running a a double carden joint rear shaft? That might be my next project.

[TonyCRD]

What if we all bugged Iron Rock to make that tri-link for the KJ?