Rear Upper Boomerang bushes - stuffed?

[cmohr]

Swamp thing had something like 6in lift, running 33's and really smashed it aboot the place, so It doesnot suprise me he broke it, he also broke some upper a-arms in the front. I wouldn't base judgement on his brakage.

There was a piccy on Lost of Neatus and his SFA project and the new rear tri-link arm in that would be fantastic for all KJ's with a lift, just cant find the pic again at the moment.

I agree Tony, would be great arm if Iron rock simply made a bolt on replacement mount for the KJ diff. or had a press fit area for a ball joint.

Glen, a double cardy, will reduce stress and vib on the driveline, even when the other models do correct the pinion angle, they still have to address the transfer case angle, so they space it or drop it down, and still use a double cardy at the transfercase end. Again, all these mods are out there in the world for a reason, just us KJ lads that are starting to realise, there is actually more to a "complete" lift than coils and big tyres.

[2JeepFamily]

I have recently been thinking about this and have pondered the idea of
modifing the upper tri link to actually have drop in it, fabricating all the
required peices
Option 1 - maybe using a Ballistic Fab 3inch Johnny style joint
instead of a balljoint. The problem is that these stlye of joints will not keep dirt and dust out creating increased wear for the type so maybe have to look into a boot of some description too.
Option 2 - Just sticking with the original ball joint.

During it all I would have locate the joint in to a position that will achieve the correct driveshaft angle at the same time, but not really a problem too extend the link a bit in fact it would work well with the drop. I will need to get my desired new springs prior so it will all be correct.
Any ideas?

[TonyCRD]

I send an email to JBA...

What if someone just welded the balljoint stud to that Iron Rock mount plate....then we would be set.

[KJ_andy]

Originally Posted by 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?

I'm at the decision making point. Replace with standard or fit a mod, I may have to wait for the answer to above.

[glend]

Andy, my Link Extension bracket is on the way from JBA ( and I have ordered the bushes and ball joint) so stay tuned I will report back. Marlin from JBA assures me that the shorter Link Extension will suit a 3"lift as it only moves the ball upward by 2.5".

I will photograph the install and flex tests.

[KJ_andy]

Originally Posted by glend

Andy, my Link Extension bracket is on the way from JBA ( and I have ordered the bushes and ball joint) so stay tuned I will report back. Marlin from JBA assures me that the shorter Link Extension will suit a 3"lift as it only moves the ball upward by 2.5".

I will photograph the install and flex tests.

Thanx Glen, standing by. I have a weeping front main as well so it'll come apart soon. The auto cooler will go on then too, got it from JBA but its still on the shelf. The new camper is in getting fouro's old wheels fitted. Should pick that up next week end.

[glend]

My JBA Link Extension kit arrived today. The install looks fairly straight forward, based on the instructions that came with it. Still waiting on the ball joint.