flushpuppyTRb

Firstly, I'm kind of new to the jeep scene, so bear with me.

i installed my teraflex BB and now whenever i hit a medium size or bigger bump i get DW, and i'd really like to know what to do to fix it. everything in the front end is tightened(not to any specific ftlbs, but tight). it has not been aligned/tires balanced since i put the lift on though.

if someone can please tell me what to do to stop it, it would be greatly appreciated!

caged

get that puppy aligned.

are your control arms adjustable?

bowdle10

get it alligned and it should go away your jeep is prolly really bad out of allignment

jonnyb78

with a 2" bb. very doubtful

wicked_xj

aliened it

flushpuppyTRb

so it seems like aligning it is the most popular response. will that for sure solve it?

sgtboom26

Take a look at your track bar bushings, my friend and I both had death wbble issues, changed out the bushing for the track bar which was ate up and now no more wobble. Not saying this is the only fix that needs accomplished but it solved mine and his. Alignment is also a good bet!

4.3L XJ

Get the alignment first, then go from there. All XJs with stock steering need an alignment after lifting

Mike1998XJ

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.

http://www.familycar.com/classroom/I...ign_Caster.gif
gearida
I worked as an Alignment guru for several years. When asked to explain or help in remembering steering angle terms I found a simple way to remember: 1) toe in and toe out - simple right if not find something else to do in your spare time...
2) Caster, my analogy is like fishing and throwing the pole from over the shoulder. This is the angle in question called caster, so if your arm is in the strong muscle man position as if you are prior to casting the fishing pole your forearm is at positive caster (strong muscle=positive)
If you are at full throw of the fishing pole or weak muscle man pose then you forearm is at negitive caster.
3) Camber, now give me some here, again take your forearms and think of them as straight up in front of you. Lean them out (as if your dates legs where apart) that is a positive...camber.
If your forearms are again straight up in front of you and your fists are coming in close together (as if your dates legs are closing) this is negative...thus negative caster.

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*

johnferg69

Yeah I'll keep that in mind

eastsider

that info should be stickied

Cherokee 4.0

x2

BOBO1234

I got the DW lastnight and I crawled under the jeep and found that I was missing one of the bolts fom the sterring stabilizer. Found a new bolt installed it and the DW was gone.

Falcon01

I've owned four Cherokee's in my life (91, 95, 99, 01) and I had the DW experience for the first time last night on my 99 Sport. Scared the crap out of me - I thought my Jeep was falling apart. After I slowed and the DW stopped, I drove another 20 miles with no problems. This morning I looked under the Jeep and found fluid leaking from the steering damper. I've seen several comments suggesting that a new steering damper will only mask the problem. My Cherokee is completely stock. Is is possible that the damper is the the sole cause of the problem, or should I go ahead and replace the stabilzer bar bushings as well? They look fine to me. Thanks.

4.3L XJ

By all means replace the damper. But before you do, have someone move the steering wheel back and forth while you look at where the track bar mounts. You probably also have a worn bushing that you should replace while you are under there.