Method to isolate cyclic slow-speed sway

dgeist · **Posted:** Wed Jan 16, 2013 3:12 pm

I've been trying to figure out a maddening slight side sway at about 15-30 mph for some time now. I really want to troubleshoot it but all the obvious checks have yielded nothing.

As I figure it, the problem could be:
a) a wheel/tire out of round, but that's not likely since I have had 2 sets of tires and rotations aplenty since it started.
b) wheel bearing rubbing slightly causing drag and sway
c) warped rotor or damaged caliper making the brakes rub, causing drag
d) an axle CV shaft binding/worn
e) a t-case drive-shaft or U-joint worn and causing cyclic wear.

I'd like to put jackstands at all four corners (outboard end of the axle tubes in the rear and under the steering knuckles in front) and look for these problems one by one in a controlled state, but one that would still allow the vehicle to sway. I figure the only variable I'm taking out of the equation is the compression of the tires (which might amplify or dampen things, depending), and the forward inertia of the vehicle (again, which might either amplify or dampen the movement depending....

It's admittedly not the safest thing in the world to run the vehicle with wheels spinning while up on jack stands, but if I'm careful (and don't go anywhere near the underside), I think it can be done with minimal risk.

Any thoughts on what I'm trying to do, if it'll work, or other suggestions to figure out the problem?

Dan

03CDKJ · **Posted:** Wed Jan 16, 2013 3:29 pm

Rear Lower Control Arms? (did you do the recall?) May need re tightening

Rear Upper Tri Link..... Bushings or boot shot?

dgeist · **Posted:** Wed Jan 16, 2013 3:43 pm

I'm not part of the recall (GA gets no salt and there's no corrosion undeneath except for a surface dusting on the axle and a couple other tiny spots). I've not seen anything out of the ordinary with the rear suspension components, but they are worth a once-over I suppose. Why would one of them cause what I'm describing if my symptoms are directly related to vehicle speed?

Dan

tommudd · **Posted:** Wed Jan 16, 2013 3:53 pm

Any time you take off, slow down, hit a groove in the road, dip in the road , culvert replacement , rail road tracks ....well any changes in the road condition at all the rear suspension moves.
So any loose parts back there will cause the rear to do a little dance shall we say. Little side ways motion, one side moving more than the other

03CDKJ · **Posted:** Wed Jan 16, 2013 3:56 pm

If you have side SWAY in the vehicle..... I would check those..... (from personal experience)
You didn't state if it was in the front or rear..... so I'm just covering all obvious checks...

If it is not grinding or making a noise... Then I would say it is possible for a bushing (which the tri link and lower control arm has) to be shot... maybe even sway bar bushings.....

Speed of the vehicle can throw a lot of people off ( you just may feel it more during those speeds)

Good luck
:JEEPIN:

dgeist · **Posted:** Wed Jan 16, 2013 4:08 pm

So, a couple things: The rubbing noise I hear is only when i'm inside a parking garage or under a bridge against a concrete wall (i.e. very faint). The front/rear is really hard to tell, it's most noticeable "in the seat of my pants" and if anything, I can only notice the swaying when the vehicle is running on otherwise very stable ground (smooth, flat, pavement). Imagine the whole jeep being a bobblehead and it feeling like the whole cab is twisting slightly one way then back the other about the long axis of the vehicle about once per second.

It's not the sway bar. Both end-links and bushings were replaced recently for other reasons with no change. Suspension parts moving is possible, defnitely, but I did a good "yank things around and check for movement/slop" when I installed my lift this past fall. Is there a decent thread y'all know of on inspection/check on the boomerang and rear arms as you describe?

Dan

03CDKJ · **Posted:** Wed Jan 16, 2013 4:17 pm

I would but Tom's probably typing it up right now..... :ROTFL:

Pry bar...... Flash light...... Stick your finger in bushing.....

Peanut butter?!?!?!

dgeist · **Posted:** Wed Jan 16, 2013 4:19 pm

03CDKJ wrote:

Peanut butter?!?!?!

That's only for getting crud of plastic body trim

tommudd · **Posted:** Wed Jan 16, 2013 4:39 pm

Long pry bar on the rear ball joint and also on the two front bushings on the tri link
I've had one that you could actually move the ball joint up and down almost an inch ( on Wildmans KJ)
Lower control arms are harder to check but on one I found it when we were tightening the lug nuts while on the ground. Lower control arms were loose enough that you could feel it when rolling the KJ back and forth just a inch or so .
After I took them out it was clear they were gone
Now if it is any of the rear LCAs or Tri link, only buy Mopar, aftermarket is junk. I can blow through them in 2-3 months

Method to isolate cyclic slow-speed sway

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