smitysjeep4x4

Would the front u Joints cuz a death wobble. I belive that they wont just very bad vibrations and if u joints did cuz a death wobble wouldnt it happen all the time not just on the highway. please help. Im getting it alighned soon so i hope that fixes the death wobble PLEASE HELP

XJ Stryker

Here is an excellent link for you regarding DW.

http://www.yuccaman.com/jeep/dw.html

Mike1998XJ

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*

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

smitysjeep4x4

THanks man thats alot of help i plan on putting my sway bar links on,then my steering dampner and getting it aligned and see waht it dose from there

funkle95xj

That has to be the most thorough explaination of death wobble I have ever seen. This is very useful information and could stand to help alot of folks out. Almost all of us will have to deal with DW at some point, and it's nice to have a clear list of things to go through to find your unique root cause for your DW.

JeepingDan

X2 I cured mine with a top quality track bar

fantic238

I have already read this somewhere else, i wonder what the source is.

Mike1998XJ

Yes, this is a compilation of various data that has been posted over time. I post it whenever I see a DW question. Rather than a bunch of single recommendatios this puts it all in one place. It helps people to understand that there is no one "silver bullet" when it comes to fixing DW. There are many different repairs that can fix DW and everyone that has it happen needs to walk through the steps themselves to uncover their own particular root cause.
We should do something like this about overheating also.
Mike

fantic238

Yes Mike it's a very good idea, i just wanted to know if the author is someone on CF or some other forum, especially for the "engineering" part.

Mike1998XJ

I don't think either one was from the CF. I think I googled Death Wobble and found the first (Engineering) one. The second one was on another forum, I don't remember which one... There is much posted on this but I like the approach these posts have. Hopefully people read these, do some investigation and then post on the CF if they are still stumped.
The only thing about these posts is they assume the troubleshooter has some degree of mechanical ability, tools such as Torque Wrenches and the knowledge of how to perform simple tests properly.
Take for example the Original poster of this post. I can't remember if he said what his degree of mechanical extertise is or if he has the tools or troubleshooting ability to carry out the details described in the text.
(Not trying to say he doesn't or can't, just making a point).
Say he reads the post and then crawls under his jeep and decides his u-joints "look" ok). Just say he only does a visual inspection. Now he might come back and post that "the u-joints are fine". All the advisors sitting at their desks operating off the information he feeds us now have misleading info). At times people ask "How did you check them" but many times people conclude that the poster has the tools and know-how to check his jeep out properly.
I see this happening all the time when it comes to overheating issues.
When someone says "I got all the air out of the system". "I checked the mechanical fan", "I replaced this or that". We, sitting at our computers have to assume they did it correctly, or not I guess.
It's too bad there wasn't a network of people all around the country who could drive over to the posters house and help them troubleshoot and learn how to troubleshoot. Maybe the poster could cover their gas money and give them a few bucks.
Comments?
Mike

shakaka

So did I, only it wasn't top quality, it was a stock sway bar. The one I got has a lifetime warranty as well so if it starts to wobble, all I have to do is install a new one.

fantic238

Hahaha, that would be awesomely smart, and also make a tv show of it, we would become rich and famous. haha.
No the fact is, i don't know if you remember when we first met on the forum, it was after a discussion about death wobble, and the person i was discussing with wrote a long post like that, exactly like that, claiming (recently) that it took him 40 seconds to type it and obviously that it was his stuff.
Do you get what i mean?

Mike1998XJ

I don't remember that post... Or who wrote it... Sorry
Mike

smitysjeep4x4

I am pretty mecaniacly inclined i put my whole lift kit on. i have year of highschool tech and im attending Unversity of northwersten Ohio for automotive high performance and ive been out her for a a year. i also brought it to a shope so they can check it out but didnt understand what death wobble was and said the only thing that looked bad was the ujoints but the ujoints wouldnt cause the death wobble only really bad grinding and vibration. i havent put my sway bar links on yet and i still need to put my steering stablizer on so after i do that i will get it aligned and see if i still have the problem.

EndlessMtnFab

I wrote a long-azz DW post a few months back. But I never said it took me 40 seconds to type it.



That was the Tire Sipe thread where I said that.



This is my version of the DW post. https://www.cherokeeforum.com/showpo...0&postcount=44


I did not get into the scientific logic behind why it is happening (like Mike does). I focused more on what to check & the process of elimination.



Joe