I could see how a bad joint could create steering feedback. I wouldn't call it "death wobble" but it can definitely make you think twice when driving.

If the joint is binding/releasing as it goes through it's range of motion, it will transmit the force to the part it is attached to. Which happens to be the steering knuckle. You can figure out the rest.



All of us have posted info on the DW at one time or another. I have some posts as well. Search smarter, not harder.




Joe

 

Have you done a transmission or transfercase drop?.? Ive heard that you have to once you go 3" and up with lift.

 

ITS BECAUSE OF GLOBAL WARMING!

I just wanted to post something even tho it has no point. Kinda like people telling you to go search.....

 

Death Wobble explained…
Here's an engineering description of DW. I get tired of seeing people guessing at what's causing their DW, so here goes. Hope it helps someone.

First, you've got to realize that the front suspensions on our vehicles were marginally stable, at best, from the factory. DW is a fundamental dynamic response mode of the entire front end...as a system. Lift and larger tires change (increase) the 'gain' associated with what becomes (or even starts out as) a marginally stable dynamic system. The damping factor (lambda) is also affected by larger tires...it decreases as a function of sidewall height/thickness ratio. Hysteresis in any control path (loose tie rod, steering box, track bar bushing) reduces the ultimate stability margin further. The fundamental frequency of DW is determined by the superposition principle where all springs involved are resolved (frame, tire resilience, hub bending, bushing deflection, etc, etc.) into one global spring constant, and all damping factors associated with friction, elastic elements, viscous damping (steering damper and shocks) are resolved into one damping factor. The natural frequency, damped natural frequency, and damping coefficient are then known. Now, if the system is overdamped and the gain is low...no problems...no oscillation. Increase the gain without increasing the damping and you go toward the critically damped, and beyond, specturm of responses. Critically damped means that DW would only 'hint' at being there, but would die out on its own without going totally unstable. This is also known as a decaying response.

Once the system goes beyond critically damped, any excitation, be it an unbalanced tire, a bent wheel, bumps in the road, etc. can set it off and the response will not decay...it will grow in amplitude, quite quickly in some cases, and may be limited only be physical non-linearities like hard stops...or breakage. That's classic Death Wobble.

A truck suspension is designed to stay in the overdamped to critically damped range. That is generally why a truck rides "rough". A Cadillac, on the other hand, is designed to stay in the undersprung range. It just "floats" down the road. Any change in the basic design parameters that affect the gain (e.g., lift, tire size, wheel backspacing, etc.), damping (tire size, steering damper, steering box condition), and hysteresis (any wear point that creates any slop) can push it over the edge and create DW. ANY ONE OR TWO of the factors discussed can do that...which is why everybody then thinks that whatever problem THEY found and fixed is the cause of all DW; it is not. It is plain and simply a marginally stable system in its original form that is easily made unstable by any of the myriad causes discussed already.

If your front end is loose (bushings, bearings, etc.) then you have a situation where your stiffness is removed and any jarring sensation (potholes, unbalanced tires, misaligned wheels, etc.) will cause the suspension to go crazy. It is no longer functioning where it is designed. On the other hand, your suspension could be very tight but an imbalanced tire would be spinning at just the right speed to throw the suspension into a unstable situation.

So unfortunately there isn't only one root cause to the problem of DW. The underlying problem is instability in the front suspension, the root causes can be a multitude of things ranging from bad/loose bushings, to loose bearings, to caster angles, to imbalanced tires, etc.

OKAY, HERE'S THE REALLY USEFUL INFO:

A steering damper only hides (maybe) the effect; it does nothing to fix the root cause.

There are two types of DW. The first typically is speed related. Whenever you reach a certain speed, bam, you get DW, no matter what. This is a vibration/oscillation issue. Look into tire balance, alignment, steering joints, missing bushings (totally shot), loose steering box (either loose bolts or worn internals), etc.

The second is an impact initiated DW. For example, hitting a pothole above a certain speed will start DW. This is more likely a bushings, loosening mounts, flexing components, etc. issue. Basically, something is tight enough that in general straight driving, it is ok, but give it an impact force, whatever is getting loose starts sliding, rebounds and starts going nuts.

Here is how you can tell if the issue is steering related or trackbar related. You are gonna need some ***** for this, but stick with me. Once you have played around with the DW awhile you find you can control it a bit by feathering the brakes. So go find a straight, deserted, bumpy road. Get the truck up to speed and get the DW going. You had it happen a few times, you have already been frantically avoiding potholes, so now go find one, quit whining. At this point, the truck is somewhat violently shaking, and you can keep enough control using the brakes to keep it on the road. Roll down the window and stick your head out and look at the front tire. What is it doing?

1. The front of the tire and the back of the tire are moving approximately the same amount side to side. In this case, the axle is stationary, and the wheel is pivoting on the ball joint during the oscillation. Therefore the problem is likely in the steering. Something in the steering has enough give to allow the movement.

2. The back of the tire is moving MORE than the front of the tire in the side-to-side movement. In this case, the knuckle is pivoting on the steering links, and allowing the axle to move back and forth under the vehicle. The problem here is most likely in the trackbar system.

This doesn't really answer a question about what's causing YOUR DW, but it should give you something to think about in your search for the root cause(s). I'd check the trac bar bushings, make sure your wheel bearings are in spec, make sure your tires are balanced, make sure your alignment is in spec - especially caster, make sure your ball joints & TREs are tight, see if you have play in your steering box, etc.

Everybody got all that? ;D
Steve
Here are a couple of Q&As I've received on another forum where I wrote about DW:

Can you explain why reducing caster helps on some vehicles? It doesn't seem like it should work, but it does.. and at other times more caster will cure it.
Basically, anything you do to get the front suspension back closer to original factory specs should help with DW. Remember, a lot of our vehicles were marginally stable from the factory, and when we lift them, change the steering, run huge tires, etc., we're making them even less stable. So, running the caster at whatever it was from the factory, along with making sure that the many other things affecting the front suspension are in good condition, will help greatly.

Unfortunately, there's no silver bullet for fixing DW, and what works for one person may not work for another. You have to consider the entire front suspension as a system and then make that system as stable as you can for the way you want to run it.

Pondering how too much caster can cause wobble, the more caster you have, the larger the vertical movement of the wheel will be, under steering input. More vertical movement = more influence that the weight of the rig can have on it, and particularly with large soft tires, that would be a fairly substantial, mostly undamped, weight hanging out there. Get it cycling, and it's not going to want to stop.

I really oughta crank down my caster a bit (front at 8 degrees) but no steering feedback = very difficult to get actual DW, so I've been lazy.
Scott, let's take it to the extreme to see why too much caster can make the suspension system unstable. Picture 90* of caster. The ball joints/kingpins would be horizontal, so when you turned the wheels they would turn top to bottom and not side to side. 90* is extreme, but the more + caster you have the more the wheels are turning top to bottom and less side to side. Besides getting pretty unstable (and VERY heavy steering feel) with much more than 10* or so, you also start scrubbing the tires pretty bad when turning with too much caster.


NOTE: For reference purposes, here is a diagram of what caster is. Positive caster is when the top of the tire "leans" toward the rear of the vehicle as depicted in the diagram.

 

should be a sticky!

 

....and the forum it came from should be credited as well.
Colorado4x4.org

 

Here's another one also... Maybe Frank can tell us all where this came from since I don't remember...


Death Wobble isn’t similar to a wobble from an unbalanced tire which is usually only felt at about 48-56 mph, DW is by far worse. When Death Wobble hits you will know… it’s a violent shake from the front end that feels like the Jeep is about to fall apart. Usually when it happens the only thing you can do to stop it is to slow down.

The first steps to eliminate Death Wobble should be a visual inspection of each component, check the bushings, the tire balance and the alignment. These are some common things you must check anytime you lift your Jeep. Death Wobble is experienced mostly on lifted Jeeps, however it is not uncommon for someone without a lift to experience the dreaded DW. Listed below are a few things you can check.

-Check your Tires
1. Out of balance tires can cause shaking in the front end, which can lead to Death Wobble. A tire/rim that has been balanced can still have internal defects that lead to DW.
2. Make sure all of your lug nuts are tight, (Sounds elementary but it happens to the best of us)

-Make sure you have a good alignment
1. After you get an alignment done, have them print out the numbers for you. An XJ should have a 7* positive caster angle. A lifted XJ can’t always have that high of a number because the pinion would become out of alignment with the front driveshaft. Pinion angle takes precedence over caster.
2. Make you sure you go to a place that will adjust the caster if necessary (either by shims in the frame side of the LCAs, or adjustable LCAs).

-Check your Track Bar, play in this can cause the axle to shake.
1. Bushings - check to see that they are not worn. Looks for cracks, and excessive play)
2. Angles - this angle should be the same as your draglink. Use an angle finders you can get at sears to determine this, don’t just eye-ball it.
3. Bolts – Make sure all bolts are tightened down to spec (some lift components have a different torque spec then)

-Check the Axle, your mounts may be worn
1. Check the axle mount. Here is a good write up on a wallowed out bolt hole
http://www.jeepin.com/features/trackbarfix/index.asp
2. Check your Universal joints, a binding or lose U-Joint can cause DW
3. On the frame end if you still use the conventional Tie Rod End or (TRE) make sure that there is no play in this, as play can cause DW.
4. Look/Check for worn/torn boots on ball joints/tie-rod ends.

-Check your Frame
1. Small cracks in the frame can cause the steering box to feel loose, Shaking from DW can only make this worse. 33’s and larger should have some form of Steering box brace, or frame brace in.
2. If you have upgraded your frame mount, make sure its cranked down nice and tight. (best to use an impact gun)
3. A busted Frame Mount can cause play in the front end causing DW (Keep a watchful eye on the welds as welds in sheer can break over time.

-The more adjustable parts the easier it is to tune in your lifted suspension.
1. Adjustable Track Bar
2. Adjustable Upper and Lower Control Arms (upper ones above 4” of lift). Not only are they adjustable, but they are stronger.


-Things to remember:
1. After any lift, get your Jeep professionally aligned, this is a REQUIREMENT, not a suggestion.
2. A Steering Stabilizer (SS) is not a quick fix for DW.
3. Make sure that the lift you purchase comes with all the required parts for a safe driving vehicle. (as long as its going to be a DD)
4. PLEASE ALWAYS DRIVE WITH YOUR FRONT SWAY BAR CONNECTED!

Entire list of everything that can cause death wobble:

-Front tires out of balance
-Front alignment out of spec
-Loose track bar
-Worn track bar bushings
-Worn track bar end
-Needing an adjustable track bar
-Bad bushings/joints in control arms
-Worn/damaged steering stabilizer
-Worn/damaged shocks
-Worn/damaged tie rod end
-Bad U Joint
-Bad ball joint
-Loose frame mount
-Steering box looseness
-Need drop pitman arm
-Driveshaft(s) not balanced
-Bad front hub assembly


Torque specs:

Item ........................................ Ft. lbs. ................... Nm

Lug nuts (1/2 X 20 w/ 60* cone) .... 85-115 .............. 115-150
All tie rod ends .....................…..... 55 ...................….. 74
Steering (both ends) ..............…..... 55 ................….... 74
Shock absorber upper nut .............. 16 ................….... 22
Shock absorber lower nuts ............. 17 ................….... 23
UCA frame end .....................…...... 66 ..............…..... 89
UCA axle end .........................….... 55 ................….... 74
LCA frame end ......................…..... 85 ...................... 115
LCA axle end .........................….... 85 ...................... 115
Track bar frame end ..............…..... 60 .................…... 81
Track bar axle end .................….... 40 ..................…... 54
Track bar bracket bolts ..........…..... 92 ...................... 125
Track bar bracket nut .............….... 74 ....................... 100
Track bar bracket support bolts ...... 31 ....................... 42
Hub bolts (3) ............................…. 75 ....................... 102
Hub- axle bolt ..........................….. 175 ..................... 237

Alingment specs (stock):

Angle ............. Preferred ........... Range ............. Max R/L diff.

Caster ............ +7.0* ........ +5.25* to +8.5* ......... 1.25*
Camber ........... -0.25* ....... -0.75* to +0.5 ........... 1.0*
Total Toe-in .... +0.25* ....... 0* to +0.45* ............. .05*
Thrust angle .... 0* to ± 0.15*

 

Ummmmmm.........JeepForum?


Jeeps Unlimited?


NAXJA?



Hell, I dunno!

 

did u get a new steering stabilizer, if u just put a lift on, the stock stabilizer is probably shot and cant handle it

 

 

 

Doesn't anyone read anymore?????????????

 

This thread is funny.

This whole thread should be on that wall of shame you want to start Frank. Theres just so many wrong answers and people takin a guess that there really isnt any good info except for what Mike posted....

Like posted above the main problems when death wobble occurs is worn steering components. Zach suggested just tightening them but that wont do good. The steering parts dont "loosen" they wear out and need to be replaced, not tightened. OR heres an idea! Have you had the balance checked on your rims lately? You could also have a bent rim that will "wobble" like that between certian speeds. Any body that could give them a good balance would be able to point out this problem.

 

it's ok to be wrong, REALLY! I was and you don't see me getting defensive and crying like a 5 year old school girl.

You are the reason people like Frankz and zachsxj stop posting and screw the rest of us who want to learn.

everyone makes their suggestion then the OP uses what he can and hopefully learns from personal experience. higher posts usually means more knowledge. I apologize to all the knowledgeable members for the all the idiots posting on this thread.

 

Nothing could be further from the truth.


Ever hear of people talking about "padding" or "post *****"




Joe