CLSegraves1

Okay, so I could use some input form some "Jeep suspension gurus". I'm having a "wobble" problem but it's not the typical "death wobble" people discuss. It's only under very specific conditions and damps itself within a few oscillations.

The vehicle:
- 2001 4 door XJ, ~4.5" lift, 32" all terrain tires
Front suspension:
- short arms with drop brackets and double adjustable rod ends (no rubber)
- WJ knuckles (link to WJ knuckle/steering build)
- double adjustable rod end toe, drag link and track bar
- track bar is ~90% length of drag link and angles are near perfectly matched
- new ball joints
- "used" hubs that feel solid (no perceptible slop in the bearing)
- no steering damper
- no sway bars (ordering an Anti-Rock front bar very soon)


I can drive down the highway at 80 MPH and the vehicle is smooth as glass. However, under the right condition I'll get a "death wobble" that within 2-6 oscillations it damps itself (again, vehicle does not have a steering damper). All I ever do is let off the gas momentarily (no application of breaks) and the vehicle at most might drop 1-2 mph before everything damps out and I'm back on the gas.

This can happen anywhere from 40 MPH to 80 MPH, but it only ever happens when the right front tire hits a BAD pot hole or in a left hand curve (with a bump). Never have an issue in a right hand turn or with the left tire hitting a pot hole. A straight ahead bump (even at 80 MPH) does not induce any oscillations.

I intend to install a hydraulic ram assist on the steering, but would love to "cure" this wobble before I do so (in case I'm masking something).

Any suggestions/insight into how to approach curing this?

Thanks,
Chris

HighOnLift

I would get a camera under the front suspension, then get in the car and turn wheel to left and right repeatedly to see if there was any play in anything at all.

90% of time, it's the track bar causing wobble, by either play by the tie rod end or where it bolts to frame (or both).


A wheel bearing will growl, but probably going to be hard to hear with offroad tires on, and would be constant, not during certain speeds or bumps etc...

If hit a bump hard enough, and track bar is weak, could cause your issues. Grab your track bar by the tie rod end... is there play or up and down movement at all?

4.3L XJ

I thought I replied to this, but it doesn't show, so here goes again. I have a WJ knuckle conversion also. I did an axle mounted track bar mount very similar to yours. However I built a frame mount that was off set enough to allow the track bar to be the same length as the drag link. When I had a shorter track bar, I had lots of problems with death wobble.



After I did this, I have had no wobble problems regardless of what I hit at any speed for the last five years

CLSegraves1

Did you click the link to by WJ knuckle/steering build? I have a hard time believing my track bar is flexing and I'm certain there's zero slop in the rod ends.




4.3, how long is your track bar vs drag link?

4.3L XJ

Exact same length and angle

CLSegraves1

Are you running a sway bar?

4.3L XJ

Yes, but it is my own design. It attaches to the transmission cross member and about half way down the long arms. It never has to be disconnected

Tsaani97xj

Does that track bar bracket on the frame attach on the side anywhere? Cant see any bolt in those pics. I would imagine if it doesnt that could be your problem. One direction is going to push it in to the frame and remain stable while the other direction is going to try and pull it away from the frame. It may give just enough play for a few cycles of DW. Nice setup btw. If it does attach and just not shown then ignore me.

CLSegraves1

Hey, yeah, it mounts using the factory bolt locations (two on the bottom of the frame and two on the outside just out of the picture's view). I can see where you are going with the thinking though and it's reasonable. As I turn left, the body tries to go right which would try to push the mount off the frame. I might give that a look tomorrow. Not sure that's the issue, but none the less thanks!

HighOnLift

What about your drive shaft? Is it possible that it is causing this?

That track bar looks beefy, Unless you have some loose nuts, I wouldn't think that is your problem with wobble.

actually I'd be more suspect of the hubs.... out of all your listed parts/upgrades, those seem to be the weakest link on paper. And a bearing going bad, could indeed cause this I think.

CLSegraves1

Drive shafts are brand new (had to have longer shafts built after installing the SYE and moving the axle forward). It's not a vibration, it's a wobble. The vehicle is smooth as can be going down the road (until the bump/turn being discussed).

Best way to check the hub? I've jacked up the wheel and tried to shake the hub (with the tire on) and it feels tight/solid (no noticeable slop).

HighOnLift

But you said it only occurs during a bump. perhaps it takes more than what you can do shaking it?

Also I've had ball joints go bad that the standard ways of testing by hand (jacking up and using a bar and lifting tire) couldn't detect.

This is just a guess, based upon your list of parts. Have you had someone turn wheel while inspecting the suspension / steering components?

HighOnLift

Also how are your control arm bushings? Do they look nice and centered too? (just going down the death wobble checklist)

CLSegraves1

I haven't, but I'll try having my wife turn the wheel tonight and see what comes of it. It's so odd that it only happens on the right side (which is why I thought it could be a hub, but the hub felt tight).

No rubber bushings in the front suspension. The control arms are DOM tube and have brand new heim joints (7/8" uppers and 1-1/4" lowers). I built them new a few weeks ago.

HighOnLift

Maybe it's the angle, but how does that track bar not move around on that bushing / bolt? Or is it just me / angle of the pic?