Crazy/Dangerous Vibrations on my 08 JK

I have a 08 JK 4-door I bought last year used that came with a mild 4” Procomp short-arm lift and 35” tires, installed at a 4WheelParts location near me.  The truck is great, however it does this one thing that scared the living poop out of me this morning.  The front end and drive train seem to vibrate and oscillate at the strangest of times.  At first I thought maybe it was a death-wobble from the lift kit being improperly installed, but now I’m not so sure.  

Prior to today, the truck would start to vibrate in both the steering wheel and the stick shift at moderate speeds- roughly about 40-50 mph range.  At first, simply slowing down or speeding up did the trick, but lately it seems to have become more pronounced.  About a week ago, the vibration was so bad, the shifter was defecting rapidly about two inches form driver to passenger side.  Today, the entire truck vibrated so bad that I almost lost control of the rig.  The only thing different about today was that I had the ESP system turned on.  So I’m stumped- what do you think? Death wobble from the lift, tire balance, driveshaft balance or a malfunctioning ESP system?  

Never did get a bite on this, but I thought I'd ask again, as I have an update.

I've pretty-much run out of things on this one.  I rotated the tires to see if it was a wheel-balance thing- Nope- still there.  I then inspected the links and the steering stabilizer for signs of wear, damage, etc, and couldn’t find any.  I took it down to my local 4x4 shop, and had them check my alignment, pinion angle and go over the whole front end.  The re-torqued the beast, took it for road test and game me a clean bill of health.

This morning while traveling at about 70 MHP on the 5 freeway, the death wobble returned, and I almost slammed into a semi.  I have a new, heavy-duty steering stabilizer on order, but I’m still stumped.  

Does ANYONE have any clues?  

check every bolt and make sure its tight, make sure all ur brackets are also tight and not loose, look at ur bushings too. to check for play, unlock the steering wheel, with the engine off cut the wheel back and fourth and have someone look and see if the entire steering moves as one peice and not seperate from each other, then bounce the front end up and down the steering wheel should not move, if it does you have bump steer and somethings prob bent, or your steering isnt paraellel enpuf  
"WHEN IN DOUBT TACH IT OUT!"

I'm currently working on a story about curing death wobble for the June '09 issue. However, since I don't want you to die between now and when the story comes out, I'll have you check 2 things that I've come across in my research regarding these JKs.

First, check your ball joints. The factory upper JK ball joint has some play built into it. It's normal for them to move up and down almost 3/8-inch, but they shouldn't have any lateral (side-side) movement. Pay particular attention to the lower ball joints. They should have zero play in any direction. My buddies at TAG Motorsports in Escondido have been noticing an unusually high number of very low-mileage JKs coming back to the shop for death wobble caused by bad lower ball joints. In most of these cases, replacing the ball joints has cured the death wobble.

Second, forget the factory alignment specs with the lift. Normally you'd dial in about 1/4-inch toe-in on a solid front axle. TAG has found that increasing the toe setting to 3/8-inch toe-out cures the death wobble in Jeeps not fixed by the ball joint replacement. They didn't even require a steering stabilizer.

Check out these 2 things and hopefully your death wobble will go away for good.

Christian Hazel
Technical Editor
Jp Magazine  

sounds like those guys at TAG know what they are doing.  
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4.5 rubi longarm, dana 44's, cromoly shafts,currie HD stering,currie antirock,warn powerplant,warn bumpers,4.88 35" creepy crawlers atlas 4 speed.

A little extra toe-in can help, but remember your tires will wear more quickly. So make sure to keep up with even more frequent tire rotations to stretch out the tire mileage.  

No - not in this case. Let's not confuse the situation. There's 2 sides of the coin - wander and death wobble.

Wander can be attributed to not enough positive caster (bottom ball joint in front of upper) and/or too little toe-in. Increasing positive caster and toe in can help a vehicle track straight and will increase its propensity to return to center when the steering wheel is let go.

Death wobble can be attributed to too much positive caster an/or too much toe-in. What happens with too much positive caster or toe-in is that each front tire is trying to track too far inward of its opposite number and they start fighting each other. Because they're linked on a solid axle, the whole front end can get to hopping and violently shaking as this occurs.

Larger tires exacerbate the problem since the theoretical angles/distances between the axle/steering centerlines and the tire's contact patch increase.  

ftgiles:
A little extra toe-in can help, but remember your tires will wear more quickly. So make sure to keep up with even more frequent tire rotations to stretch out the tire mileage.

Not really any more tire wear. We're talking about 1/8 of an inch more toe (3/8 vs. 1/4).  

Again, confusing the situation.

The JK fix was to go from the conventional 1/4-inch toe-IN to 3/8-inch toe-OUT.  It's a difference of 5/8-inch.  

My alignment shop here in Phoenix also says that sometimes a toe-out can help a big tire'd, lifted Jeep. He likes to play around with the alignment spec with reagard to each individual Jeep's combination of lift and tire.

He always starts with "minimum caster, maximum toe". But sometimes ends up with minimum toe and even toe-out sometimes.

He also always says, make sure you keep your tires rotated religiously, because uneven tire wear can contribute to the problems.  

Thanks Christian; I'm more book smart that street smart when it comes to troubleshooting.

I'm throwing her up on jackstands today, and I'll look over the balljoints/check them for play.  If I deceid to have them fixed by TAG Motorsports, is there anyone I should ask for?  

If you're in So. Cal, then they're in Escondido, CA. www.tagmotorsports.com

Jay Miller heads the shop and is the one who figured out the alignment deal on the JKs. I'm sure they'll be able to fix you up.  

Jay miller is a good guy to know he helped me out with allot of things on my rig and even invited me on a little outing to Parker AZ where we had a blast.  
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4.5 rubi longarm, dana 44's, cromoly shafts,currie HD stering,currie antirock,warn powerplant,warn bumpers,4.88 35" creepy crawlers atlas 4 speed.

Okay- update- Threw the truck up on jack stands and checked for play in the upper and lower ball joints.  It seemed that everything was fine (very slight play in the upper, and the bottom was solid).  The visual inspection was a bit more showing; the driver side is fine, but the passenger side looks to have an odd wear pattern in the middle of the rubber fitting, parallel to the ground.  I think that it’s safe to assume that something is working this ball joint a bit harder than it should.

I ended up throwing on the new stabilizer anyway (after all- two bolts, and I had it) and the issue seems to subsided for now (or at least it did this morning- I’ll know more as I continue to drive it).

I’ll give Jay a call (as soon as I’ve freed-up some Jeep funds) and see about getting it replaced.  Is there a heavy-duty aftermarket version I can swap in?

Thanks!  

Right now there's no HD ball joint upgrade. I sent some worn JK ball joints to Dynatrac in Huntington Beach for analysis, however I haven't followed up to see if the company is actively pursuing a HD ball joint upgrade.  If they do I'll let you all know.

-Christian