I just broke a SECOND upper rear control arm. The first time happened on some of the more challenging lines on Back way to Crown King in AZ last fall. That was the driver's side. And Monday on the Rubicon I broke the passenger side. Both parts broke in exactly the same way - the fwd bushing eye snapped off; not exactly at the weld, but just beside it, making me think the metal was heat-fatigued during the welding process.

When the first one went I considered it a fluke. But now the same thing on the other side? Hmmm....

I'm running the orange Poly bushings from AB; I'm now suspecting they are the contributing factor here. Enough-so that I don't think I'll be replacing those bushings w/poly in the future.

Just a little food for thought.

We usually talk about front control arms, but does anybody know if the RRS (and what years) REAR control arms interchange and if so, are there any differences in either the bushings or the control arm itself? I was able to get a used part to do a trail-side fix and keep moving but the bushing in that part are soft. Tomorrow I'm going to try to locate a new part locally so I can get it installed and get the truck re-aligned in time for my next trip. Unfortunately that means I need the part by this weekend, so time is tight.


Oh, and just so you know an LR3 has now run the Rubicon all the way through. Story to follow.

 

Wow sorry to hear about the failure but glad you got outta there. It's reasonable to think that the harder polybushes are transmitting more force to the control arm. Looking forward to reading your write-up on the Rubicon. Pics!!!

 

I wonder if the steels under designed with the rubber bushing as the engineered fail point

Iirc lucky 8 wheels their lr3 with trashed rubber bushings to see how long till an arm breaks

 

I heard one downside of poly bushings when used on leaf springs is the frame cracking because the bushings absorb some of the force which poly instead transmit.

 

Looking at things it appears the failure is due to the welding causing some heat related problems at the eye. The weld itself does not fail, but the metal just beside it. Also of note there is a gusset on the rear most bushing eye but not on the forward one which is the area of failure, so I suspect a combination of poor design (no gusset), poor manufacturing (heat control when welding), and higher transmitted forces due to the poly bushings.

Regardless of all that, today I replaced both the upper and lower control arms with new RRS parts. They are actually the same control arm as the LR3, just with a revised (firmer) bushing installed. Tomorrow I hope to get it aligned, then on the trail again Friday.

 

Some pics - this week:

 

And last fall in AZ-







Looks pretty similar, eh?