Unstable Swaying at highway speeds - JeepForum.com

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post #1 of 22 Old 07-26-2010, 12:47 PM Thread Starter
jackitorslamit
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1996 ZJ 
 
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Unstable Swaying at highway speeds

Issue: Recently While going highway speed 60-75 mph in my 96 ZJ with RE 3.5 lift, when I switch lanes I feel the vehicle sway to the point I have to slow down. It happens when I switch lanes and start to straighten the steering wheel out it feels as if I over corrected and I get a swaying motion. This is a new problem since I have had the lift on since 2004.

Recent work: Just recently, I had all new shocks replaced (bilsteins 5100), new tie rod ends and drag link, new steering stabilizer and new tires. The issue did not arise until I had an alignment done when I got the new tires (32 in Kumhos)

Searches: I have read that possible problems could cause this:
Tire pressures: tired airing up and down... slight change but still sways
Loose track bar bolts Frt and Rear: Everything is tight
Loose bolt in steering: everything is tight
Shocks: new and bolted down tight
Tires: balance and running straight

Only thing I can think of is the alignment may have been done incorrectly. I tried a different shop since they had installed my tires and this tech didn't give me a read out of what was changed. So I will be going back to the guys who usually do my alignment who have never failed me before.

If anyone has any other ideas, please let me know.

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post #2 of 22 Old 07-26-2010, 01:08 PM
bigbossd1030
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Take a look at your swaybar links and swaybar.
Make sure it looks good and is not loose.

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post #3 of 22 Old 07-26-2010, 01:30 PM
MurdaJs
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Since it happened only after an alignment, my first guess would be that the castor is off. I had a similar swaying when I went up from 3.5" to 5.25 lift in the front on stock arms. I adjusted the castor moving the axle as far forward as possible, which helped the swaying but introduced driveshaft vibes.

I would take it back to the shop and tell them how the swaying started only after the alignment. Hopefully theres room for adjustment for castor
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post #4 of 22 Old 07-26-2010, 01:31 PM Thread Starter
jackitorslamit
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Sway bar bushings front and back new and links all nice and tight.
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post #5 of 22 Old 07-26-2010, 01:35 PM Thread Starter
jackitorslamit
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Yeah, I talked to the shop and since I waited over a week. They said I probably have hit something to knock it off. So they wont be getting anymore business.

I have a feeling that the tech messed with the castor, when there was no need to, trying to get it to factory specs. Probably never done a lifted vehicle before. So I am taking it back to the place that usually does my alignments and who always get it right the first time.
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post #6 of 22 Old 05-06-2012, 05:51 PM
PaYj
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ok i know i am opening up a old thread but wondering if this problem has ever been solved, i just purchased a 96 zj with what i believe to be a 3.5 lift, has rustys lower arms. When driving down road the jeep sways left and right, i replaced a ball joint already and a hub bearing thinking that was problem no fix, i took it to get a alignment and they said the toe was off and fixed it, but they could not adjust the caster, which i come to find out you can, my caster is at 8.8-9.1 is this to much caster and is possibly causing my problem??
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post #7 of 22 Old 05-06-2012, 06:37 PM
MurdaJs
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I dunno about your caster, but how do the trackbar ends/bushings and control arm bushings look? If any of those have play, that could be the source of your problem. Our trackbar brackets are notorious for wallowing out, like my rear currently is
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post #8 of 22 Old 05-06-2012, 07:29 PM
PolkaPower
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Control arm bushing shot? Castor can be the issue as well.
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post #9 of 22 Old 05-06-2012, 08:11 PM Thread Starter
jackitorslamit
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My problem ended up be a really bad alignment. Had a buddy of mine pull it up on his alignment rack and once pulled up we both saw the toe was really off. Once that was fixed all was good. Good luck
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post #10 of 22 Old 05-06-2012, 08:20 PM
TheHalfWit
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Quote:
Originally Posted by PaYj View Post
ok i know i am opening up a old thread but wondering if this problem has ever been solved, i just purchased a 96 zj with what i believe to be a 3.5 lift, has rustys lower arms. When driving down road the jeep sways left and right, i replaced a ball joint already and a hub bearing thinking that was problem no fix, i took it to get a alignment and they said the toe was off and fixed it, but they could not adjust the caster, which i come to find out you can, my caster is at 8.8-9.1 is this to much caster and is possibly causing my problem??
9 degrees of caster, and you're wondering if its a problem?

Norm is closer to 6.0-7.5 iirc, so yea I'd be willing to bet that 9 degrees of caster isn't doing anything to help matters.

I'm wondering, do you have adjustable control arms? Because I don't think the stock cam adjuster bolts have that much adjustment in them. (If it has adjustable arms no regular alignment shop will touch it other than toe.)

Calm. C.

If a week goes by without needing to replace something, pinch me because I must be dreaming.
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post #11 of 22 Old 05-06-2012, 08:32 PM
MarkInTombstone
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You changed tire size but did you change the rims and check the back spacing to correct your tire scrub to the road?

You'd be doing me a favor if you called me Mark or Tombstone, but not both.
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post #12 of 22 Old 05-06-2012, 10:25 PM
moldeck
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could the sway issue be an adjustment needed in the steering gear box? Just asking.
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post #13 of 22 Old 05-07-2012, 01:18 AM
TheHalfWit
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Quote:
Originally Posted by moldeck
could the sway issue be an adjustment needed in the steering gear box? Just asking.
Actually that makes me remember something, caster won't cause swaying I had mine at 12* of caster for a bit before I put my springs in and it went straight and true.

But a defective steering box can cause wandering, search the boards since I remember a thread on rebuilding your box from a while back. (I'm on my idevice or I'd search for you )

Edit: I suppose a better way to say it though is that excessive caster shouldn't cause swaying, but unequal caster might. (I haven't experimented with that one, the excessive caster was just an experiment to see how it handled with arms in and adjusted for the springs. (But without the springs.)

Calm. C.

If a week goes by without needing to replace something, pinch me because I must be dreaming.
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post #14 of 22 Old 05-07-2012, 08:07 AM
PolkaPower
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There is positive and negative castor. There is no excessive castor. Think of how motorcycle forks are raked back. That is positive castor and it's also what keeps the bike going straight down the road. If the forks were zero vertical or raked forward(negative) the bike would be all over the road and much harder to control.
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post #15 of 22 Old 05-08-2012, 02:54 PM
PaYj
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I understand the motorcycle idea more rake is stable at higher speeds, less like a rocket had better turn in and handling. My toe was off they fixed that but said they could not fix my caster. I checked all bushing and joints. With jeep on ground I can not find anything that has play except wheel bearing and ball joint which I replaced. The guy took it for a test drive and said that the swaying unstable feeling was from to much caster, which confused me cuz I always thought to little caster caused unstable feeling

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alignment , bolt , sway , Tie rod end , track bar

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