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Unread 04-29-2013, 07:00 AM   #1
engineerd
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Front End Shimmy Under Braking

I had a slight wobble between ~50-60 mph that was starting to get worse. After looking through the forum, the most likely culprit looked like the track bar. Saturday morning I checked the track bar and the bolt on the axle bracket was slightly loose. I tightened it up and the shimmy is very nearly gone. It was time for a tire rotation anyway, so I took the truck to Discount for the free rotate and balance figuring it wouldn't hurt.

Now, if I brake from 60 to 50 mph I get a violent wobble in the front end. After searching the forum the most likely culprits appear to be the following:

1. Improper lug torque warping the brake rotors
2. Warped brake rotors (these rotors have about 20,000 miles on them now)
3. Bushings and rod ends

Considering this bad shimmy ONLY happenes between 50 and 60 mph, what is the most likely cause? I'm going to check lug torque tonight.

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Unread 04-29-2013, 08:31 AM   #2
EvolutionXJ
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Does the steering wheel vibrate left and right when braking? If so then yea probably warped rotors. Which can be caused by over tightening the lug nuts. And can also be caused just over time by uneven wearing brake pads that will eventually warp your rotors
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Unread 04-29-2013, 09:01 AM   #3
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Quote:
Originally Posted by Evolution92 View Post
Does the steering wheel vibrate left and right when braking? If so then yea probably warped rotors. Which can be caused by over tightening the lug nuts. And can also be caused just over time by uneven wearing brake pads that will eventually warp your rotors
It definitely vibrates, I'll have to pay attention to whether it's up/down, left/right, or all over.
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Unread 04-29-2013, 12:26 PM   #4
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I had this problem a while back and cured it by getting the rotors machined (and new pads).
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Unread 04-29-2013, 03:28 PM   #5
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Control arm bushings can give you problems like this under braking as well. Had the same problem before I swapped in my new LCA's. Im sure its a combination of a few things together causing you grief.
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Unread 04-29-2013, 03:41 PM   #6
engineerd
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Quote:
Originally Posted by VegasGT View Post
Control arm bushings can give you problems like this under braking as well. Had the same problem before I swapped in my new LCA's. Im sure its a combination of a few things together causing you grief.
That's what I'm thinking. I've removed the track arm as a cause. Now it's down to warped rotors (either due to heat or improper torque...completely possible if the guy at Discount had his spinach that day) and/or bushings/rod ends.

I'm going to check the torque when I get home and eliminate that as a cause, though if the rotors are warped that usually presents itself at all speeds, not just a narrow bad. That leads me to bushings....

Thanks for all the help and ideas!
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Unread 04-30-2013, 05:31 AM   #7
EvolutionXJ
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Not completetly true with the rotors. Higher speeds show issues that aren't noticeable at lower speeds. For example if you tires arent balanced correctly then you probably won't notice till on the interstate.
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Unread 05-01-2013, 09:14 AM   #8
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Originally Posted by Evolution92 View Post
Not completetly true with the rotors. Higher speeds show issues that aren't noticeable at lower speeds. For example if you tires arent balanced correctly then you probably won't notice till on the interstate.
You're right. I'm experiencing the issue only between 50-60 mph. Braking problems wouldn't necessarily go away at higher speeds.

The shimmy showed up again this morning while cruising, not just braking. So I'm thinking it's definitely bushings and/or track bar related.
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Unread 05-01-2013, 09:31 AM   #9
EvolutionXJ
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Yea if you are experiencing issues while just cruising then I'd check the bushings first
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Unread 05-01-2013, 07:34 PM   #10
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Thanks!

You all have been helpful!
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Unread 06-06-2013, 08:17 AM   #11
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Just to close the loop with everyone that responded. I took the Jeep in to the shop to see if they could diagnose it. The tech working on it said that usually he suspects the steering damper with these symptoms, but mine looked brand new (it's an OME damper I put in about a year ago). He checked ball joints, etc. and the only thing he found was a bad universal joint in the right front hub.

I picked it up and it still had the wobble. I finally had a little bit of time a couple weekends ago to get under the front end and check things out for myself. The track bar was a little loose on the axle end, so I tightened it up. Everything else was tight. That didn't fix it.

So, I took it back to the shop. The same tech looked at it and checked bushings, etc. Nothing was standing out. So, we decided to change the steering damper to a stock replacement part. That fixed it!

So, now I'm going to email OME and just let them know I had a failure after 1 year. I don't expect (or really need at this point) a new one. I just want to let them know.
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Unread 06-06-2013, 11:58 AM   #12
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That didnt fix it it only a bandaid. I would be pulling my caliper pins and slicking them up with antiseize as it sounds like they aren't floating as well as they should. A rotor would have to be super warped to honestly feel much if your calipers are floating the way they should
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Unread 06-07-2013, 06:24 AM   #13
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Originally Posted by Jeep_Tech View Post
That didnt fix it it only a bandaid. I would be pulling my caliper pins and slicking them up with antiseize as it sounds like they aren't floating as well as they should. A rotor would have to be super warped to honestly feel much if your calipers are floating the way they should
Since it was presenting itself during cruising, not just braking, I don't think it is necessarily brake related.

After talking with ARB, I'm convinced the steering damper failure was caused by something else. I'm down to 2 possible causes:

1. The track bar axle mount bolt hole got opened up somehow and so even though the track bar is tight, it can move. This is the easiest thing to check at this point.

2. Control Arm Bushings.
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