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Violent Shake? Any help?


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Installed 1 3/4" coil spacers, new shock, new stearing stabilizer, new sway bar, and had the tires balanced over the weekend. Everything went ok, however, now when I hit a bump in the road with both tires I get a violent shake up front, the greater the speed, the worse it is. If the bump in the road hits both tires at the same time, no problem, the problem happens if there are bumps that hit one tire then the next. Before the lift, there was a little bit of it going on, but I figured it was the worn out shocks and steering stabilizer.

 

Any help or suggestions would be greatly appreciated.

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Did you get the front end alligned?

 

No, does not pull in either direction and runs right down the middle of the lane.

 

Just because it doesn't pull doesn't mean it is aligned. Check your toe specs and see what you get. You want it a little toed in. I usually just get a buddy and hold a tape measure on the front side of the tires between two equal lugs, then do the same behind the tires. I go with 1/2" toe in as a max.

 

I've gotten death wobble with no noticeable pull in either direction.

 

Also check your ball joints.

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Your experiencing death wobble (or known as DW). DW is a situation where the front axle begins oscillating with such violence that control of the Jeep is difficult until slowed down, and the entire vehicle shakes to the point you feel it will come apart.

 

It can be caused by many things. Some of the most common are;

 

- Bad TRE's on the tie rod.

- Unbalanced wheels/tires.

- Bad bushings in the control arms.

- Bad trackbar mount/bushing/tre.

- Bad balljoints (not as likely though).

 

 

Since you said you've had your wheels/tires balanced I'd first check the TRE's on the tie rod as well as the condition of your trackbar. Those tend to be the most common, followed than by the control arm bushings.

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Your experiencing death wobble (or known as DW). DW is a situation where the front axle begins oscillating with such violence that control of the Jeep is difficult until slowed down, and the entire vehicle shakes to the point you feel it will come apart.

 

It can be caused by many things. Some of the most common are;

 

- Bad TRE's on the tie rod.

- Unbalanced wheels/tires.

- Bad bushings in the control arms.

- Bad trackbar mount/bushing/tre.

- Bad balljoints (not as likely though).

 

 

Since you said you've had your wheels/tires balanced I'd first check the TRE's on the tie rod as well as the condition of your trackbar. Those tend to be the most common, followed than by the control arm bushings.

 

Thank you for the information. How do I check for this condition, or am I better off going to a shop? I am not very educated in this field.

 

Thanks again.

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Do you by chance hear a bang or click type noise come out of somewhere up front when u hit a bump. Ive had the same problem and i was able to reduce the intesity of the DW with new Unit Bearings but i still have it. I think that it is my control arms but I'm thinking about upgrading the whole steering setup and new control arms b/c I'm running stock control arms with a 3-4" lift (i was NOT the genious to keep stock control arms with that much lift (PO):roll:)

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Do you by chance hear a bang or click type noise come out of somewhere up front when u hit a bump. Ive had the same problem and i was able to reduce the intesity of the DW with new Unit Bearings but i still have it. I think that it is my control arms but I'm thinking about upgrading the whole steering setup and new control arms b/c I'm running stock control arms with a 3-4" lift (i was NOT the genious to keep stock control arms with that much lift (PO):roll:)

 

No noise at all. Actually drives and rides like a dream, UNTIL I hit a series of bumps...

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Just because it doesn't pull doesn't mean it is aligned. Check your toe specs and see what you get. You want it a little toed in. I usually just get a buddy and hold a tape measure on the front side of the tires between two equal lugs, then do the same behind the tires. I go with 1/2" toe in as a max.

 

 

X2 on checking toe. I had basically the same issue with mine, and finally got the tape measure out. I was toed in an extra inch :oops: Reset it to 1/2" and not a wiggle since....

 

Jeff

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Just because it doesn't pull doesn't mean it is aligned. Check your toe specs and see what you get. You want it a little toed in. I usually just get a buddy and hold a tape measure on the front side of the tires between two equal lugs, then do the same behind the tires. I go with 1/2" toe in as a max.

 

 

X2 on checking toe. I had basically the same issue with mine, and finally got the tape measure out. I was toed in an extra inch :oops: Reset it to 1/2" and not a wiggle since....

 

Jeff

Two things where also affected, your alignment as Jeff just said as well as CASTOR!! With solid axles the more you lift the more positive Castor the axle wants. Notice how the rear portion of your front tires are now closer to the bottom rear edge of your wheel well. That shows the Castor you have LOST with the lift.

 

Check everything Motion pointed out and be DOUBLY sure of your tire balance. Sounds like this didn't change and I am assuming that the DW didn't occur before the lift. So its most likely been brought on by something you changed.

 

CW

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I shoulda mentioned that I readjusted the caster with longer fixed lowers and adjustable UCA's. When I first lifted it, I only used the fixed lowers with stock UCA's and had to remove the front DS due to horrible pinion angle. Adjustable uppers solved that problem, but I had to dial in the best length......it's a delicate balance between pinion angle and caster (which can only really be solved completely by rotating the knuckles). I ended up at around 4.5-5 degrees negative caster, and the driveshaft doesn't bind. Steering feel is a bit "vague" with the little caster, but it's livable.

 

The only issue I have now is a small camber issue due to the axle tube being rotated more forward than stock. I'm considering offset balljoints.

 

Jeff

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Since he only installed 1-3/4" coil spacers up front, I think the caster can be corrected easily enough with a couple of 4mm shims behind the LCAs. You can get these from the dealer, p/n 52003976 for about $1.50/ea. I'd concentrate on the things Motion mentioned mostly, like the TREs and track bar bushings. Get it all tight, then get it aligned.

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Even if the tires are out of balance with DW you typically still have other issues. The out of balance tires is just what helps the DW get going. The root of the problem typically is something else.

 

Unless the person who balanced the tires is a smuck and they are WAY off balance I don't think that the tires being a "little" off is going to the root of the problem. It's most likely one of the other things we mentioned above.

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I shoulda mentioned that I readjusted the caster with longer fixed lowers and adjustable UCA's. When I first lifted it, I only used the fixed lowers with stock UCA's and had to remove the front DS due to horrible pinion angle. Adjustable uppers solved that problem, but I had to dial in the best length......it's a delicate balance between pinion angle and caster (which can only really be solved completely by rotating the knuckles). I ended up at around 4.5-5 degrees negative caster, and the driveshaft doesn't bind. Steering feel is a bit "vague" with the little caster, but it's livable.

 

The only issue I have now is a small camber issue due to the axle tube being rotated more forward than stock. I'm considering offset balljoints.

 

Jeff

 

Holy cow!!! 4-5 degree negative cannot be your actual setting. I don't thing you could get the DS attached!!! I wanna say 6 positive is factory spec. Currently I am at about 7-8 degress positive.

 

 

CW

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Pull your lower control arms first check the bushings , if all cracked and look shi**ty either change them or go to a longer lower arm, that is half inch too 3/4 longer . This is a problem that you can chase for a while but this is your best place to start . I have had this 2 times on different vehicles xj zj mj all to different degrees , does your ride have over a hundred thousand miles ? If so this is the best place too start .

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positive...negative....I get confused every time I think about it (too much fruit in the beer will do that to ya, you know 8)?) Mine's rotated in the same direction as yours is, just not as much :D

 

Isn't the factory spec something like 7-8 degrees? You're just about spot on, CW.

 

Jeff

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Missed that CW. XJ/MJ specs are 6*-10* POS caster (wheel forward of vertical) at least according to the antique machine at my friends shop. I have mine set at 8* POS, but I don't have the front driveshaft pinion angle to worry about either. :D

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Death wobble has got dick to do with pinion angle , a pinion will either vibrate or remove your u joint if weak !

True, but there is still a relationship, because when you lift you DECREASE the caster angle while you INCREASE the u-joint operating angle. The more you adjust the caster to try to get back the positive caster, the more you increae the u-joint angle. Once you get to about 4" of lift or higher, you basically can't run the correct caster angle without gobbling u-joints, so you have to back off on the caster and hope you don't have death wobble problems.

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Death wobble has got dick to do with pinion angle , a pinion will either vibrate or remove your u joint if weak !

 

Lifts 101. When you lift your rig, the top of the diff rotates forward, the wheels rotate backward. To negate these effects the lower control arms need to be lengthened, i.e. more + caster. Caster and front pinion angle on lifted rigs is a compromise to find the ideal pinion angle so the u-joint working angle is within specs and does not cause vibes, and the caster is pos enough to have good straight line steering. And yes vibes are not DW, but they certainly contribute to it. So pinion angle does have dick to do with DW. Get real.....

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Eagle I can tell buy your response that you have never had the fun of death wobble , a vibration is one thing DW is a complete different thing . Pinion angle has nothing to do with DW . I would love to to have had it that I could just remove the front drive shaft a problem solved that is not how it works , I get so sick and tired off being outbuilt and outwheeled by people that never that never built or wheeled anything except a computer chair !!!!!!!!! To the young man that asked the question start at your lower control arm bushings and come up from there.

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Pinion angle has nothing to do with DW .
That is not really true either. Incorrect pinion angle causes the camber & toe to be off as well and definitely will contribute to getting DW started. If there are weak points such as control arm bushings, ball joints, track bar bushings, loose track bar etc, etc... then you are in for a ride that is not any fun at all. I can't speak for Eagle, but I have dealt with it several times and the solution has been different in almost every case. Some had to do with pinion angle/castor/camber/toe and some where assortments of the afore mentioned items.

 

Correct alignment is always the first step in my process of fixing DW and in doing a correct alignment...castor (ie; pinion angle) is adjusted. :cheers:

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