Violent front end shakes over 50mph

[rockwerks]

well my butt of the truck is also low which is something I've been told to fix ASAP and see if it helps. My rear is 3" lower than my front because I installed 2.5" lift spacers in front and extended shackles in back but the rear lift total was minimal to the front. I have a set of 3" blocks I still need to install to level it off but I am having trouble finding U bolts for a Dana 35.

Also ordered a kit to reinstall my swaybar with new bushings.

Then what?

Oh, and i CAN get over 55mph on a smooth as glass road, it is bumps, even minor ones that trigger the DW....

then its not wheel balance LOL and thanks for the further info. I would check for bad ball joints, its easy to do jsut jack up the truck one front wheel at a time so it is about 1/8" off the ground, use a block and pry far on teh front f teh tire to lift up on the tire/wheel and look for play in the ball joints, and it can be just one bad joint too. ya just gotta watch for any play

Any custom spring shop will have or can make the u bolts for ya.

 

[MaXJohnson]

A marginally out of balance tire unlifted is magnified 10 fold when lifted because the inverted y geometry the higher you go the less stable.

Where did this "10 fold" rule come from? How does the inverted y geometry affect tire balance?

Could this be the long sought after xjnation secret key to Death Wobble?

 

[rockwerks]

Where did this "10 fold" rule come from? How does the inverted y geometry affect tire balance?

Could this be the long sought after xjnation secret key to Death Wobble?

reread you will be tested later

 

[HaZakated]

Sounds like you could have some worn outer bearings.

jack up each side of the vehicel seperatly, and put a large screw driver under the tire. Then pry up. If there is play in the wheel, sure enough, you have bad bearings. Easy fix, unless you have a later model XJ. The bearing unit is one large sealed unit that will cost you upwards of 100$ a side to replace. Easy job, just expensive.

Just a thought...................

Brian

 

[Eagle]

Easy fix, unless you have a later model XJ. The bearing unit is one large sealed unit that will cost you upwards of 100$ a side to replace. Easy job, just expensive.

???????

ALL XJs have unit bearings, except a very few early 2WD vehicles. This is not limited to "later model" XJs.

 

[HaZakated]

Eagles right....I guess I just assumed the older models had open bearings.

Anyways, If there is alot of play in your wheels, that would be the problem.

oh, and if that is the problem and you replace them, make sure and use some anti-sieze compound gel around the new bearing housing ring before you install.

Brian

 

[91 4.0XJ]

Does it have a steering dampener? If it does, check it to see if its leaking. All it is, is a shock and when its cold out the oil in it is thicker and it will work better. When it worms up the oil will be thiner and it wont work as good. Just my 2 cents.

 

[MaXJohnson]

Does it have a steering dampener? If it does, check it to see if its leaking. All it is, is a shock and when its cold out the oil in it is thicker and it will work better. When it worms up the oil will be thiner and it wont work as good. Just my 2 cents.

yuk!

what kind of vision does that put in your head

 

[91 4.0XJ]

lol, sorry. I cant spell.

 

[rockwerks]

yuk!

what kind of vision does that put in your head

LOL I hate worms in my steering!

 

[Rev Den]

Does it have a steering dampener? If it does, check it to see if its leaking. All it is, is a shock and when its cold out the oil in it is thicker and it will work better. When it worms up the oil will be thiner and it wont work as good. Just my 2 cents.

Nice theory...but...the steering stabilizer will not cause death wobble.

Rev

 

[91 4.0XJ]

How would that not cause it? What is the purpose of the steering dampener? Not trying to be a jerk, but i have seen it cause this. Im sure other things can cause it too, but dont say it CANT cause it.

 

[Rev Den]

How would that not cause it? What is the purpose of the steering dampener? Not trying to be a jerk, but i have seen it cause this. Im sure other things can cause it too, but dont say it CANT cause it.

I understand. A steering damper will hide the problem...but not fix it. Many run without dampers and have no DW. If you need a damper to solve your DW you are just hiding the problem...not fixing it, the cause lies elswhere. A steering damper is to smooth the feedback into the steering wheel from tire contact with objects on the ground surface.

The statment stands and is correct.

Rev

 

[rockwerks]

I understand. A steering damper will hide the problem...but not fix it. Many run without dampers and have no DW. If you need a damper to solve your DW you are just hiding the problem...not fixing it, the cause lies elswhere. A steering damper is to smooth the feedback into the steering wheel from tire contact with objects on the ground surface.

The statment stands and is correct.

Rev

X2 This whole thing is getting old maybe time for a DW sticky

 

[Eagle]

Before tempers get any more frayed in this thread, let me toss out some bits for consideration. I've been in contact with MaXJohnson, our resident suspension engineering guru, and I think we have sort of agreed that there's a problem of terminology at work here. Semantics rears its ugly head -- again.

In just about all the DW threads we have ever head, people talk about "cause" and they talk about death wobble -- which is the "result," or the "effect. We are brought up and educated to think that way, right? CAUSE ==> EFFECT.

But as we've found from numerous threads about DW, it ain't that simple. There are many factors at play, and some of those factors are considered the "cause" by one person but not by another. Example: A bad steering damper "causes" DW. Then other people chime in and report driving for 100,000 miles with no steering damper. Ergo -- a bad steering damper does not "cause" death wobble.

MaX and I have at various times used a third term as part of this scenario, and maybe we should put it on the table and hope it gets more widely accepted. Let's call that term "trigger." To me, the trigger is a causative event.

What do I mean? When I'm in a rush, I frequently post that bad wheel balance "causes" death wobble. I'm willing to agree with MaX that this isn't strictly true. I have had one wheel with a slight shimmy for a lot of miles at times, and it never escalated into death wobble. Why not? Dunno -- but it just never set up that oscillation harmonic that MaX wrote about earlier in this thread.

Death wobble is NOT wheel shimmy. One wheel can shimmy and you can still drive at 65 MPH, so it ain't death wobble. What IS death wobble is when a shimmy or shake in one wheel is transmitted to the other wheel, and the two begin oscillating in a harmonic relationship that causes the intensity of the oscillation to increase. So in a technical sense we could say that the ROOT CAUSE of death wobble is the solid axle/coil spring front suspension.

But then we need something to start the ball rolling. That's what MaX and I sometimes call the "trigger." The "trigger" may be a tire that's badly out of balance, or it may be a bump or a chuckhole in the road. It's whatever starts one or both wheels wobbling. I think "causative event" is a good way to describe it, but let's use "trigger" as a shorter way to say the same thing.

So now we have a root cause (suspension design) and we have a trigger. There are numerous things that can (and do) work to counteract the root cause and the trigger, thus preventing a "trigger" from resulting in death wobble. Tight bushings, ball joints and tie rod ends for example. A good steering damper, for example. An alignment with enough caster angle to weight the shoulders of the tires for example. Good tire balance, for example. These are all factors which resist, or "mask," the onset of death wobble. None of them actually cause death wobble, but absence of one or more can allow a trigger to escalate into death wobble.

I know this was long, but I hope it results in better understanding and fewer arguments over terminology.

 

[HaZakated]

x=CAUSE y=(effect)Death Wobble z= exact problem(mechanical disorder)

(x1 leads to y+z)
y=specificly Death Wobble
z=unknown?
x=unknown?

General statement: if all the info you have provided is accuate, I believe that z=outer wheel bearing hub unit is worn out. Check for symptoms first, but I have a feeling it is this. If the wheel is tight and doesnt have play, I'll take the F. Sounds very familiar to the same prob I had about 3 months ago.

Brian

 

[JJacobs]

Excellent post Eagle!

 

[jeepguy97]

When it worms up the oil will be thiner and it wont work as good

You are all wrong......Its those dang blasted worms. :laugh3:

 

[MaXJohnson]

Great post, Eagle. You have a knack for presenting information in an easy to digest manner.

It really would be great if we all could look at death wobble in terms of cause, trigger and control. By doing so, you can see that eliminating one trigger, such as tire balance, still leaves you susceptible to other triggers because the cause is still there and the control is not. Minimize the cause and you minimize the need for control. Maximize control and you can withstand a trigger event.

For an example, I can change the natural frequency of my front suspension(cause) by replacing my 33x12.50's with some 33x10.50's. Both sets of tires are dynamically balanced and reasonably true (round). The heavier mass of the 12.50's lowers the natural frequency of my suspension to the point that it is stable when I hit a bump at 50MPH. With the lighter 10.50's, the natural frequency moves up to a less stable range and will consistently go into Death Wobble on bumps that don't phase the 12.50's. With enough damping (control), I can run the 10.50's, but I know DW is lurking in the background.

To work on the cause, I can change tires, wheels, axles, swaybar, suspension link angles and design, etc.

To work on the trigger, I can avoid nasty bumps and expansion joints, make sure my wheels are straight and tires are dynamically balanced and round, brake rotors are true, etc.

To work on the control, I can make sure all suspension and steering joints are tight and well maintained, bushings are in good shape and the steering stabilizer is doing its job, particularly in the short stroke range.

To control the worms, I can use my spell checker

 

[jblaze5779]

Mine kinda did something liek that and it turned out to be the steering stabilizer