I had no way to recreate the noise in my RC arms either except by driving it. I ended up tightening the joints as tight as I could get them with their spanner wrench and the clunking went away.
Well ****. I'm an idiot.
After going though the entire front end again with a microscope and "fixing" 5 or 6 things that I think were within' tolerances for a ****ing rocket engine, I got pissed off, pulled the CA's again, and tightened the driver upper until I broke the spanner. Then I made a BETTER spanner and tightened it more. Then broke the new indestructible spanner on the lower driver, and built an indestructible x2 spanner and cranked down the other two.
...
Jeep rides like a ****ing luxury car.
Like, my XJ has always ridden unreasonably nice on street considering where it takes me off road, but with precisely zero suspension noise, it's almost eerie to drive.
Now, I had to crank them on VERY goddamn tight. I can't imagine there's anywhere for grease to go at this point, but I guess we'll see. I sorta suspect the ball cups are going to just tear themselves apart the first time I hit the trail, but maybe they won't. The cups look fine on visual inspection, but it's entirely possible they're just worn beyond tolerances on the inside of the sphere. It's a fairly hard poly, so it could just be that when I crank down the spanner, it's just trying to compress the outer part of the cup, and the inner just has a lot more room than it should. I'm tempted to just grab a rebuild kit from RC just so I know. I'm also tempted to fire-bomb RC's shop, but given what I've put the arms through, I suppose I should be surprised they're even still holding onto my Jeep. I want to complain about the design, but I KNOW damned well that a heim joint would've eaten itself in the first wheeling trip (conditions in the PNW seem to LOVE heims, but not in the way we want). I've never had a heim from any manufacturer stay tight (on my track bar) for more than a month or two.
So, problem solved, but now it's engineering time. I think a sealed, greaseable heim is the right answer, but through all this, despite finally getting my XJ to the pinnacle of Jeep (There's really nothing left to do to it as it goes wherever I point it), I'm actually starting a new build on top of a first gen 4 runner frame (which makes me feel like a bad person, but easily 75% of the work that went into my Jeep was to make the unibody hold up to my abuse).
Anyhow, so let that be a lesson to anyone with the same issue I guess? I dunno. **** you control arm joints. I have defeated thee.
