Hi All

It seems like there have been a million threads on certain violent reactions of JKs to bumps in the road. Some people call this a shimmy, some people call this a bump steer, and some people call this a death wobble. I have read most of the threads regarding these issues. Personally, I don't care what it is called, I just want it fixed (although a separate post defining each of these would be really helpful, PLEASE DON'T DO THAT IN THIS POST) and I need your help. Here is what I have.

I have a 2007 JK unlimited with a 2.5" Terraflex BB (the one with spacers and shock extenders). I have LT265/75/R16 BF Goodrich all terrains on stock 16 inch wheels. I have a terraflex swaybar disconnect and that is it for modifications to the suspension and tires. The tires are balanced (at least last time I checked), and both trackbars are torqued to 125lbs.

I have had the lift on since July 2007 with no issues until Aug 2008 when I picked up the "issue". Since then I have driven my jeep about 1 a week to move the fluids around (moved to DC and take the metro) and haven't gone wheelin' (been really busy with work).

Here is the problem.

When I am traveling down the road, at any speed, if I hit a large bump in the road, I get a violent shake that feels like it is coming from the front end. The wheels feel like they are wobbling back and forth. When I slow down, the violent shake stops and the jeep drives like normal again. This does not happen at a specific speed, it is caused by bumps in the road.

The solution?

I am letting you all know what I have tried so far so that everyone knows where I am.

1. Trackbars tightened to 125lbs (they were already there)
Result = no change

2. Had the front end aligned. Here are the final numbers
Caster
Left = 2.5
Right = 2.4

Camber
Left = -.5
Right = -.3

Toe
Left=.10
Right=.10

I am going to drive the jeep today on known problem spots and I will let you all know the results, assuming I don't crash my jeep trying to make it vibrate.

I know that there are a million different things to try but I am trying to come at this from a logical manner so that I am taking a very specific progression through the possible solutions.

One other thing to note is that when I took it to the shop the mechanic said the steering stabilizer was shot so I am going to have to replace it. I am going to take the jeep out today with the changes to the alignment to see if that makes a difference. Based on all of the threads, if the death wobble, bump steer, vibration, (whatever you want to call it) has been resolved, the steering stabilizer won't matter.

On a final note. Please don't take this thread as trying to insult anyone or upset them in any way. I truly appreciate all of the individuals on this site that are trying to help. Reading through some of the threads, I know tensions can get heated from time to time, but it seems everyone is trying to help out. Thank you all for the assistance!!

 

Did you cloesly examine the trackbar brackets for any signs of fracture or fatigue? It is sometimes hard to see, but a can of compressed air shot closely near a suspected crack can sometimes help to make it show up by squirting the air through thae area, cracks will show condensation where it comes through.

Doesnt always work but it can, just dont shoot anything into your eyes, i.e. Wear goggles.


If your stabilizer is leaking, then i would certainly replace it, but that wont fix the problem. It will just cover it up until it fails again. It is possible you had the issue before, but your stabilizer was masking it, and now that it piddled fluid, it isnt anymore, thus making it noticable.

You said you had no issues, then suddenly you did. Do you recall doing anything that might have been the catalyst? Offroading around that time frame? hit a big pothole, pedestrian, old lady in a wheelchair? *L* Really, if you can remeber, it might help.

Could be tires out of balance, but that is more speed related, so more likely something else (ie centered around trackbar) are the ball ends ok? any play there?

Out of curiosity, did you check out the rearend as well?

 

I don't recall the exact catalyst other than that it happened right before I came to DC. There wasn't anything that stands out (not four wheeling or anything like that). I want to say the issue has always been on the road and hitting a bump. It is possible that the problem was always there and simply covered by the SS but that is why I am going to try to take it out today. I probably wont fix the stabilizer until I get a good feeling that the problem is gone.

I have not checked the trackbar for cracks but when I took it in for the alignment I was there when both the mechanic were looking at it and they both said it looked good. Neither of them looked at it closely. I might try to check that out after the trip today.

The only thing that I have done to the rear is make sure the track bar was torqued correctly.

Thanks for the suggestions.

 

new update.

I took the jeep out for a ride today to see if the changes to the alignment helped solve the problem. Unfortunately, they didn't. It seems now the the problem becomes apparent at about 50 mph and up. Below that at between 40 and 45 mph, the jeep wobbles for a second and then recovers.

I also checked the trackbar from breaks or cracks and didn't see anything. In fact, all of the joints looked good.

So here is the current changes and results

Trackbar adjustment = no change

alignment = no change

Any thoughts on the next step?

 

your not going to believe me any more than i believed anyone else, but have your balance checked,

seriously, it took 'em 4 times to get mine right and it shut off like it was never there once they got it right. (my shake/wobble/shimmy dance turned on abruptly at 40, shut off just under 50) it would show up from time to time, especially if i caught a bump on a corner, but since they got the balance, it was gone.

Creeping back in now though, i was aired down a while back and i think i spun a tire on the rim & my balance is hot again.

 

My caster is at 4.2 and 4.4...almost twice his.....is mine high or is his low?

Could that be his bumpsteer problem?

 

certainly possible, but rarely see much of a problem with that on a 2.5" BB. Every Jeep has it's own quirks though, so it could be.


(I was opting to try all the cheap fixes first)


I ma not positive of the numbers, but 4 seems a lot closer than 2 & change.

 

First off your caster is WAY too low. This is most likely due to your lift. Get a set of adjustable lower front control arms and set your caster to at least 4.2

Secondly you might want to remove the track bar and check to see if the holes in the track bar mount are wallowed out. If they are, you will need to weld washers over them. Also check the track bar bushings at this time.

 

Thanks for the thought so far. To recap here is what I have for recent suggestions.

1. Get the balanced rechecked
2. Adjust the caster to at least 4.2 with a set of adjustable lower front control arms.
3. Look a at the track bar to see if the holes are wallowed out.

A couple of questions thoughts on each of these:
1. Balancing. I will do this but wouldn't this be an issue that would cause a vibration everytime I reached a certain speed, and not just when I hit a bump?
2. Is there a less expensive way to adjust the caster. I want to limit the variables in the suspension as much as possible before I start adding parts. Hellbound, if I recall from the other posts you were running stock right or at least no lift. Where you able to adjust this another way?
3. I will have to take the track bar off on the weekend when someone can help out. But that is a good idea (seen that in the other posts). Maybe I can get them to do this at a shop.

Thanks all, please keep the ideas coming.

 

1. I never thought balancing would effect bumps, only speed variable shimmy but others have posted otherwise, so I don't know.

2. There is no other way to adjust your caster, short of using CAM bolts and from what I have heard you want to AVOID cam bolts. I bought a set of TF lowers.