Death wobble despite trying (almost) all solutions

[br1anstorm]

There is no evidence that a worn, even missing, steering damper will cause, or contribute to death wobble. Many people, including myself, do not have a steering dampener installed; it's really not needed, and if it appears to help, it's merely a "band aid", covering up the real culprit.

Yes, xjbubba, I was very aware that the steering damper was unlikely to be a primary cause of DW, and that replacing it might not help but could disguise the problem. That's why I didn't replace it until after I had already done the shocks, the bushings, the UJs and checked alignment and wheel balance. I now find it interesting that even a brand new steering damper doesn't cover up the DW, which is still as bad as it was!

Not sure how you determined "the ball joints are well within tolerance", but I can tell you worn ball joints can cause, and are a major source of death wobble, as are worn track bar bushings/rod-ends, and worn tie-rod and steering linkage. At 130K miles, any and all of those front axle steering and control arm bushings are probably shot.

We pryed the ball joints with a crowbar while in place - no slack. Then we looked at them on the bench - they were sound. If my rally-car building engineer colleague, whose professional workshop we use, tells me they are good, then they are good.

As for the bushings, I have replaced them all (see earlier posts in this thread) with Daystar polyurethane ones, and also fitted new tie-rod ends. So it's clear that the problem isn't with wear in any of them. In fact there's a theory (see separate discussion with heyhar) that these hard new bushings might be one cause of the trouble!

Neither front or rear drive shafts can cause death wobble. But, to satisfy yourself without spending money (that is if you are doing your own work), just remove the "suspect" shaft and go for a ride.

Thanks for that reassurance. Neither I nor my engineer buddy thought the drive shafts were responsible for DW (though I've seen some DW checklists which include "out of balance driveshafts" as an item to check). But if I get utterly desperate, I will take out both shafts and see what happens!

 

[br1anstorm]

Re: Death wobble - perhaps we blame polyurethane bushngs?

I've re-read this post, and I don't see evidence that you've gotten rid of those horrendous urethane bushings

No, the red ones are still there, mainly because I have no others at present - the old ones were thrown away, and I haven't yet plucked up the courage to visit the bank on my way to the dealer to pay for a whole set of OEM rubber ones. But it may yet come to that. It would be a real pain if it turned out that these new firm bushings actually cause DW, when most folks - like xjbubba and many others - suggest that worn bushings are to blame!

One trick to try is re-tighten the hell out of the control arm nuts and bolts. ........ And, whatever you do, when you're cranking down suspension nuts and bolts, the weight of the car must be on them. lest you turn them into little springs of their own, exasperating the problem. Good luck, and report back!

I'll have another good look at the way the red ones are fitting in place and I'll try a bit more cranking. When installed, they were hand-tightened on the workshop lift and fully cranked with the weight on the wheels, so I'm pretty sure we have avoided that kind of "pre-loading" problem. Would it be worth trying a partial return to OEM rubber bushings, just for the upper and lower control arms (leaving the red poly ones in the other places where we fitted them ie in the sway bar mountings, TREs etc)?

Thanks, once again, for helping me grapple with this. I hate having a problem that I can't diagnose! But at least all this discussion might also help others, since DW is such a plague for so many of us.

 

[heyhar]

Re: Death wobble - perhaps we blame polyurethane bushngs?

Would it be worth trying a partial return to OEM rubber bushings, just for the upper and lower control arms (leaving the red poly ones in the other places where we fitted them ie in the sway bar mountings, TREs etc)?

Yes, most definitely!! The sway bar bushings and link bushings, tie rod boots, etc. are just fine-mine are still in, squeaking like crazy. But, and I'd be willing to bet a pint at your favorite pub, that it's the control arm bushings causing your heartburn. You mentioned going to the dealer-They're going to clean you out. Check out Quadratec or any one of a number of aftermarket sources for these types of items. We've got Crown control arms, from Qtec, in all four of our XJs, and they're just fine, at a fraction of what the dealer wants for them. I'll bet that even with overseas shipping, the cost is still less than a dealer. Don't do just the bushings, buy the complete control arms. The cost of the bushings alone is comparable to the complete arms. The only separate bushings will be the front uppers, at the axle end.

Now you see what I went through when we had an MGB back in the seventies.....

 

[White Knuckle]

Tires - keep them rotated/balanced and make sure you spray all the mud out after trail runs. Some aftermarket rims have bad runout and cause balance issues, even when professionally balanced. Some tires are bad too.

Geometry - this is the biggest problem I see with DW cases. If your jeep isn't lifted, it doesn't mean your geometry is good. You springs sag over time.

Shock bushings - probably the most overlooked. I went nuts over this one once. Finally replaced the eye bushings because I noticed the shocks were loose. Ended another bout of DW.

Ball joints - They are not hard to replace, just more involved and time consuming. JUST DO IT. I finally pulled mine and I shouldn't have even waited half as long - they fell apart!!! Haven't had a problem with DW since, even with bad geometry, except when I had mud dried in the wheels.

Damper/stabilizer - I'll say it again: This was put on at the factory to reduce BUMPSTEER. I ran without one for many years. Does little for DW. I'm not going to argue about this. Yes, I put one back on so the ride would be more pleasant on these potholes for my carpool riders.

Tie rod ends - you should be replacing these at regular intervals anyway. Get good ones, or they will be worthless as soon as you drive away.

Track bar - get a good one with a solid joint and a vertical mount bracket. Tie rod ends on a trackbar just don't make sense. Make sure the axle mount hole is tight.

Bushings - already been covered. I had some made with an "off-compound" and it was a pain dealing with the manufacturer.

I had some tricks for driving with DW, but they vary between vehicles. Nothing is ever "good enough" until the problem is gone.

 

[amcjeep]

i just fixed mine. dw at 56-65 mph. it was the control arms, the bushings were worn out, and the caster was going positive at speed. the key was... that is was only 1 degree neg caster at curb, but was like 0 degrees at speed, causing a the shakes... replaced all, 4 control arms with rock auto arms.. then a proper thrust angle alignment... ok now. by the way, the DW got worse when i replaced the shocks and steering stabilizer. it put more pressure on the control arms...

 

[amcjeep]

Geometry - this is the biggest problem I see with DW cases. If your jeep isn't lifted, it doesn't mean your geometry is good. You springs sag over time.

that was the case with mine... a 1986 amc.

 

[br1anstorm]

....it was the control arms, the bushings were worn out, and the caster was going positive at speed.... replaced all 4 control arms with rock auto arms.. the DW got worse when i replaced the shocks and steering stabilizer. it put more pressure on the control arms...

This thread is throwing up some interesting and diverse ideas, suggestions and possible solutions.

But can I try to clarify one thing about control arms? It's similar to the exchange I had with heyhar about the track bar.

The control arms are pieces of steel. As such, they don't wear out. They could get bent by serious impact (but you'd know and see that!). Metal fatigue, or rusting through....is unlikely. The issue with control arms, just like the track bar, is all about the mountings and bushings at each end, which DO wear, and flex, and perish.

If that is so, then the problem, and the solution, has to do with the bushings. The only reason why people replace the complete UCAs or LCAs - unless I have missed something - is because new complete arms come with preinstalled new bushings, for not much more than the cost of new bushings alone, and complete new control arms are perhaps easier and quicker to fit than changing out all the bushings and keeping the OEM arms.

OK - so as I have replaced all the bushings on all the UCAs and LCAs, and checked the geometry (on a Hunter machine), how come I still have a severe problem?

So far, the only theory on the table is heyhar's: that polyurethane bushes are to blame - for being too hard and so reinforcing, or transmitting, the oscillation once it starts. But we still haven't nailed why and where the DW begins... and indeed why the new shocks, and new damper, and new bushings, don't absorb, or contain, the wobble.

I'm still trying to be systematic and logical in working through the diagnosis in order to pinpoint the source of the problem. Haven't got there yet, though I've tried almost all the cures the witchdoctors have suggested!

 

[br1anstorm]

Re: Death wobble - sagging springs?

Geometry - this is the biggest problem...Your springs sag over time.

Presume you mean the (front) coil springs? How soon and how seriously do they sag in normal use? They are rarely mentioned in the DW catalogue.

Rear leaf springs will of course lose some of their "springiness". Mine have. But surely a sagging rear doesn't cause a wobble at the front?

(Hmm - perhaps I need to rephrase that before the witty responses start appearing!)

 

[Sonex522]

I've read a lot of posts about DW and it seems odd to me that a For Certain, This is definitely it fix hasn't been found. Here's my noob ramblings...
I have a 2000 XJ 4.0 4wd, bone stock, 80,000 miles, and I have no death wobble. When I bought it, the track bar rod end was shot so the thing wandered badly, but no DW. The shocks are getting iffy and I'm pretty sure the control arm bushings are bagged. I have some mysterious clunk when accelerating. I replaced the track bar and had a toe adjustment done, but I still have a wandery, heavy steering Jeep, but no death wobble whatsoever. And I have no steering damper mounted.
With motorcycles, death wobble is fairly common. It's called a tank slapper. It's usually precipitated by a bump like a big lane groove that grabs the side of the tire contact patch. Bikes with bad steering bearings tend to get it if the trail distance (caster in car terms) gets too small when the front wheel is pushed aft. To understand the physics, visualize a line through the steering stem, all the way to the ground. The tire's contact patch needs to be behind the point where the line intersects with the ground. Move the line aft (bad bearings, big bump, etc.), and stability goes to zero. Grocery cart wheels have a ton of trail, so they're quite stable.
I wonder if the Jeep DW issue could be related to caster. The axle is attached to a pretty flimsy unit body. Maybe over time, the upper body mounts move forward in relation to the lower ones, reducing caster.
When a tire encounters a bump, the contact patch moves forward briefly, which reduces stability. Suppose one side of the contact patch hits a bump. Now the tire is getting steering force from the bump and caster forces. If the tire steers, the other side of the contact patch gets moved way forward, making the caster situation even worse. I would guess that the tire starts crab walking on its contact patch.
If I had tried all the standard fixes and nothing worked, I'd probably try a fairly extreme caster increase and see what happens.

 

[amcjeep]

@ sonex
YES !!!

 

[amcjeep]

the original caster spec was 7 degrees, but it was changed in 1994 to 4 degrees eliminate pull to the right. i have mine set to 7 and it does not pull. most alignment shops have the shims for the lower control arms...

 

[xjbubba]

Doubt "0" caster would cause death wobble; certainly would exacerbate front-end in-stability. Some vehicles came from the factory with 0* caster. When I first built and installed my front axle, the caster was ~3*--only noticeable effect was "wandering"; had to "stay on top" of steering at all times, no "one-finger" cruising. "0" caster could be good for a road racer--steering very responsive to driver input.
Death wobble is nothing new. I had death wobble on my 1931 Model A Ford. The culprit was worn king-pins---which is analogous to worn "ball joints".

 

[br1anstorm]

Re: Death wobble - it's not incorrect caster angle

In exploring the possible causes of DW, this thread might yet become the longest one in the forums!

I got briefly excited when Sonex522 posted about caster angle, as his tech analysis seemed credible, so I quickly checked the printout from my most recent alignment.

Damn.... caster on my Jeep is almost exactly 7 degrees. So the severe DW it still suffers is not because of insufficient or incorrect caster.

The search continues. I've already changed almost all the components in the front suspension, and I hate replacing what seem to be perfectly good parts just on the half-chance that one of them might be the cause of the DW. Almost the only things left to change are the control arm bushings (take out the new polyurethane ones which heyhar doesn't like, and put in new OEM rubber ones) and - if I am to go with xjbubba's advice - the balljoints (even though the existing ones appear to be fine).

Then all that's left are the coil springs (do they really sag?), before I have to think about messing with the rear leaf springs and shocks which are original and have 100k miles of wear.

 

[heyhar]

Re: Death wobble - it's not incorrect caster angle

Almost the only things left to change are the control arm bushings (take out the new polyurethane ones which heyhar doesn't like, and put in new OEM rubber ones)

The reason there may be confusion about control arms vs. bushings, is that when you buy control arms of the OEM type, you get nice, new rubber bushings in them. Costwise, it isn't worth the time to buy just the bushings, as swapping new bushings into old arms just isn't worth it. The only bushings you should have to swap are the two upper fronts, at the axle. I'm still convinced that your problems arise from the non-compliant urethane control arm bushings. I've been there.....

 

[frank bryant]

Does anyone really ever figure out causes dw ? my 96 had a lite case a few weeks ago ! I knew it had saggy springs and the shocks where toast ! so I installed a rough country 3 in kit with spring packs and shocks and stabilizer well guess what it shakes so bad now and then that I about wont drive it ! like, you I have checked everything and cant find 1 thing that makes me think "oh there it is" ! I drove it 70 miles yesterday at 65 and 70 and it drove and rode like a dream ! today I made 2 miles out the hiway and had to put a tire in the grass to get control ! I m so fustrated I could cut it up for scrap
!:huh:Hasta

 

[br1anstorm]

Re: Death wobble - now I'm going to change bushings again...

....when you buy control arms of the OEM type, you get nice, new rubber bushings in them. Costwise, it isn't worth the time to buy just the bushings, as swapping new bushings into old arms just isn't worth it. .... I'm still convinced that your problems arise from the non-compliant urethane control arm bushings. I've been there.....

OK, next question for heyhar or anyone else to comment on. I iunderstand that getting complete replacement arms has a certain logic. But over here, replacing all the control arms (upper and lower) with their OEM rubber bushings included, is a huge cost, whether from the dealer or by ordering from a US supplier like Rock or Quadratec (because of the cost of freighting such bulky, heavy, items to UK).

If I'm going to get rid of the Daystar polyurethane bushings, I have a choice: either to order the OEM rubber ones from the local UK dealer, or to get a set of MOOG bushings from an aftermarket supplier in UK.

I haven't yet done a comparison to see the price-difference. Question is - what are the MOOG ones made of - rubber, polyurethane or something else? Would they be better or worse than going back to the OEM Jeep ones?

 

[heyhar]

Moog would be a good choice. They make probably the best OEM parts. Just what they're made of, I'm not sure, but I'd bet it's not urethane! The arms that Qtec sells are made by Crown, and the bushings are made of a similar material to the originals.


Question is - what are the MOOG ones made of - rubber, polyurethane or something else? Would they be better or worse than going back to the OEM Jeep ones?

They would be a good choice.

 

[br1anstorm]

It's been a while since I updated this thread on my DW problem. That's partly because I have been working on other minor niggles on the Jeep and major problems (seized a/c compressor!) on one of my other cars.

But there are a couple more small bits of "evidence" to add to the mix. I have had the Jeep down in the rally-car workshop and out on the road. As we have checked and dealt with most of the major and obvious possible items on the DW checklist - like track bar, shocks, and steering damper - we are now looking for smaller and less obvious things. Here's the latest update:

• there is a small leak from the steering box (the Jeep has power steering), which I presume means the bearings and/or seals are worn. There is some obvious play in the UJs in the lower steering column, but that is surely normal. Also a tiny but visible amount of play in the shaft coming out of the steering box which connects down to the Pitman arm. Could this be a possible DW cause?
• the outer tie rod end at the LH end of the steering rod (the one that connects to the knuckle) has a little bit of play: more movement than any of the others, which don't have any play at all. So I'm going to replace it;
• we looked again at the ball joints, upper and lower. The existing, original ones really are fine. I know some posts in this thread say change 'em anyway.... but my rally-driving engineer says that is a waste, when there is nothing wrong with the ones I have!
• one other weird symptom. Just sporadically, when turning right on full lock, there is a nasty recurrent noise from somewhere down on the LH front. More a crunch than a click: I can almost feel it through the soles of my feet. If the UJ hadn't been replaced, I would suspect it, but then again, a UJ makes a clicking sound all the time on full lock if it is bad. This noise only occurs some of the time. And I can't make it happen in the workshop when wiggling/turning the wheels or the steering on the ramp. So where might this noise be coming from?

Meanwhile I am getting a replacement set of used UCAs and LCAs with worn but OEM rubber bushes included, off a scrap vehicle. I shall put them on in place of the original arms, which now have red polyurethane bushes in them. This change, which heyhar has urged on me, might not be a cure, but I want to see if this changes the DW behaviour at all....

This might yet turn into the longest DW thread on the forum!

 

[ManyInchesOfFury]

Re: Death wobble - now I'm going to change bushings again...

I haven't yet done a comparison to see the price-difference. Question is - what are the MOOG ones made of - rubber, polyurethane or something else? Would they be better or worse than going back to the OEM Jeep ones?

The control arm bushings are rubber, I just bought and replaced all of my front end bushings for about $120 shipped from Rock Auto. All MOOG. The sway bar and track bushings are poly though. The poly control arm bushing completely eliminated my DW. Added new shocks and the only vibe I have is my tires because they have ridiculous lugs on them.

And I also put a new OEM track bar, didn't cure my DW. Only the MOOG poly track bar bushing did. I think its like $15 and your front axle wont budge a bit from left to right. Also a wheel out of balance will help cause your DW over bumps. I had found out after I replaced my track bar bushing that my wheel was out of balance, since the previous owner's Pro Comp X-ATs didn't cause a bit of wobble all the way to 100. I know because I rode with him (only to 70 though, lol. 100 in a XJ with 230k miles is a death wish).

 

[CharlesS]

It's been a while since I updated this thread on my DW problem. That's partly because I have been working on other minor niggles on the Jeep and major problems (seized a/c compressor!) on one of my other cars.

But there are a couple more small bits of "evidence" to add to the mix. I have had the Jeep down in the rally-car workshop and out on the road. As we have checked and dealt with most of the major and obvious possible items on the DW checklist - like track bar, shocks, and steering damper - we are now looking for smaller and less obvious things. Here's the latest update:

• the outer tie rod end at the LH end of the steering rod (the one that connects to the knuckle) has a little bit of play: more movement than any of the others, which don't have any play at all. So I'm going to replace it.

A worn tie rod will likely be the source your the problem.... The worn tie rod will allow the front steering to load and unload causing a cyclical movement of the tires known as Death Wobble....