Death wobble is trying to come back

[Knucklehead97]

Well it was too good to be true apparently... Jeep had no issues the past few months with going smoothly down the road as fast as I wanted. But today I was going about 55 and all of a sudden I felt it try to go into a wobble-spree. Slowed down and it still had a slight wobble too it but didn't go full Death Wobble on me. Tomorrow I'm going to check to make sure everything's tight under there but I'm thinking I'm gonna have to look into it a little. Everything has been replaced with beefy parts except for my steering, which was replaced about a year ago with ZJ V8 steering (Moog brand). Upon adjusting my toe in when I lifted, I did find one of the tie rod ends to be spinning and I had trouble tightening it due to it spinning inside the housing. Think this is where I need to start? Also, should I just go through the trouble of upgrading to 1 ton steering? I find it ridiculous that the Moog has already burnt itself out...

[yxmj]

Tires have been balanced after all work was done?

[Knucklehead97]

7 minutes ago, yxmj said:

Tires have been balanced after all work was done?

Brand new tires balanced when they were mounted. Set toe in and caster angle myself per the instructions I was given on here. Control arms swapped with aftermarket ones, RE double shear Trac bar, new hubs, sway bar links replaced with adjustable quick disconnects, and Bilstein shocks.

[HOrnbrod]

Which TRE is spinning when you try to tighten it? And what was the Moog p/n?

[gogmorgo]

Make sure all the fasteners are tight for your control arms.

When I bought my ZJ the PO said he hadn't been driving it because of death wobble. Just driving it around the block at under 20mph I could tell something wasn't right. Got underneath, and the bolts at the ends of the double-shear track bar had about 1/8" or so under the head and nut. They'd been torqued to spec, but the track bar came with distorted-thread nuts, and the run-down torque hadn't been accounted for. I couldn't actually get at the axle end nut because of where it sits (might be a low-pinion thing) and I ended up having to weld a flag onto the nut to hold it in place while torquing the bolt.

I'm not saying it's necessarily your problem, but it's a thing that could happen.

 

I'm not 100% on the tie-rod end endlessly spinning being totally normal, but they will need some degree of rotation to allow for steering. You may be able to very carefully hold the upper portion of the taper with needle-nose vicegrips to prevent it from spinning so you can torque it down properly, but you do run the risk of damaging the surface the boot seals against so that's probably a last resort. 

[Eagle]

1 hour ago, Knucklehead97 said:

Brand new tires balanced when they were mounted. Set toe in and caster angle myself per the instructions I was given on here. Control arms swapped with aftermarket ones, RE double shear Trac bar, new hubs, sway bar links replaced with adjustable quick disconnects, and Bilstein shocks.

 

Then the tires are probably the cause. I've been through this twice on my XJs. New tires, mounted and balanced at the tire shop, get on the highway at about 55 MPH and the front end starts to shimmy. Never gets to full death wobble, and if I speed up to about 62 MPH or faster it smooths out again.

 

Take them back to the shop, they balance them again ... same issue. I have a friend (former XJ and MJ owner, currently has a ZJ) who works as a shop foreman at a VW dealership. Both times, he took the tires and balanced them for me and they've been perfect ever since. Too many techs these days don't know how to use the tire machines. I had one shop tell my my Jeep factory alloy rims were bent so they couldn't be balanced. My friend put them on his shop's Hunter machine and he said the wheels were perfect. The "technicians" at the other shop didn't even know how to attach a wheel the the machine, why should I expect them to know how to balance a tire?

 

Here's a clue: This has been true ever since I can remember, going back to my mother's 1958 Rambler station wagon: for some reason, tire balance issues ALWAYS manifest at 55 MPH. If you can drive through it and it smooths out above 62 (or so), it's not a death wobble or suspension issue, it's a tire balance issue.

[DirtyComanche]

Is that TRE tight or not?  If it isn't, fix that first.

[Manche757]

I routinely drive 65 on way to work. If i hit an expansion joint, i might get a shimy in the front end but clears itself. The only time I have had full blown death woble was when the air pressure in tires had gotten way low. I pumped them to 34psi and it did not happen again. If you have done all that you indicate, you might experiment with diff psi in front end tires. Has anyone replaced all of the front end with a nonMJ front end since it must be a design flaw

[Eagle]

15 hours ago, Manche757 said:

I routinely drive 65 on way to work. If i hit an expansion joint, i might get a shimy in the front end but clears itself. The only time I have had full blown death woble was when the air pressure in tires had gotten way low. I pumped them to 34psi and it did not happen again. If you have done all that you indicate, you might experiment with diff psi in front end tires. Has anyone replaced all of the front end with a nonMJ front end since it must be a design flaw

 

Why "must" it be a design flaw? I currently own three XJs and three MJs that I have personally driven significant distances, plus a 2001 XJ that I sold to a friend awhile back. Among all of them, I probably have close to half a million miles racked up. I bought my first XJ in early 1988, so that's more than 30 years ago. The original '88 XJ alone has 287,000+ miles on it. Out of all those miles, the only one that ever experienced death wobble was the red '88 MJ. The death wobble occurred when it had the 4" lift installed (later removed) and when I had it on 31-inch tires. The cause was tire balance, and the cure was to put a different set of tires on it.

 

Solid front axle vehicles are inherently more prone to death wobble than independent suspension designs, but that doesn't mean there is a design flaw in the Jeep solid axle design. It just means we should not make a bunch of changes without being aware that changes may have consequences.

[HOrnbrod]

8 hours ago, DirtyComanche said:

Is that TRE tight or not?  If it isn't, fix that first.

 

11 hours ago, Knucklehead97 said:

Well it was too good to be true apparently... Jeep had no issues the past few months with going smoothly down the road as fast as I wanted. But today I was going about 55 and all of a sudden I felt it try to go into a wobble-spree.

 

Upon adjusting my toe in when I lifted, I did find one of the tie rod ends to be spinning and I had trouble tightening it due to it spinning inside the housing.

 

If there was no wobble for months then suddenly started, it's not tire balance unless a ton of weight fell off at once. Or you have square Walmart Goodyear tires installed. 

 

A TRE spinning is not normal. I've never had one. Fix/replace this first. Then check the others too.

[Eagle]

1 hour ago, 75sv1 said:

I have 1 ton Chevy cross over steering, WJ Big Brakes,  Rusty's OTK Trac bar. Still Death Wobble. Didn't have it before this stuff. I do not have the steering stabilizer on it. I'll Tire PSI. I am at 4.5 lift, with Rusty's (I think) Adjustable control arms. I did have it aligned and at that time the tires were balanced. I think that is when it started. I did replace the motor mounts with Brown Dogs. It had ripped apart the stock motor mounts. Still, my question is raising to 4.5 lift, and 31 inch tires, would the alignment specs be different than stock? Also, it seems my steering gear box has loosened up. I replaced it about a year ago, and had about a 1/16 play. Now about 1/8 or more each side. I did get a Borgeson steering shaft, not installed yet.

 

Yes, the alignment specs may be different with a lift. You didn't list all the components you used to get your 4.5" lift.

 

In the XJ/MJ front suspension, caster angle is adjusted by adding or removing shims at the rear end of the lower control arms, to push the LCA locations forward or back, thereby rotating the axle tubes and changing the tilt angle on the Cs and steering knuckles. That's what caster angle is -- the tilt in the forward-to-aft axis of rotation of the ball joints.

 

Positive caster is when the lower end of this axis is forward of the upper end. Positive caster is what helps generate good tracking at highway speeds, but it is also important in preventling death wobble. So HOW you achieved your lift and what alignment specs were used is important. The effect of just adding a lift, without replacing the LCAs with longer or adjustable LCAs or adding a lot of shims, is to reduce the caster angle. If you reduce the caster angle significantly, you greatly increase the probability of experiencing death wobble.

 

This is why so many aftermarket companies sell adjustable LCAs. Even then, you get into a delicate balance. With taller lifts, you're also messing with the U-joint angles in the front drive shaft. Trying to put the caster angle back to within factory specs with a significant lift results in excessive U-joint angles. Consequently, you have to search for the sweet spot between a caster angle that won't kill your U-joints and a caster angle that will be enough to prevent death wobble.

 

There has been a lot written on this topic, both on this forum and on NAXJA.

[Knucklehead97]

They're Cooper AT3's so not cheap Walmart tires at all  I'm going to check the tightness of everything today and will probably order new tie rod ends. The one that was spinning is the long solid one that connects to the drag link down close to the passenger side tire. I did get it tightened down enough, but feared it was shot anyways. I forgot to add that a year ago when I put the Jeep under the knife to be lifted and fix the brakes (master cylinder blew so I went with a WJ set up) the Jeep did have full on death wobble at 45-55 MPH. I drove it like this for about 30 miles and I feared the wobble destroyed a few steering parts.

[Minuit]

2 minutes ago, Knucklehead97 said:

They're Cooper AT3's

 

I know this probably isn't your problem, but a few years ago I bought a set of those and had two of four be severely out of round.

[Knucklehead97]

1 minute ago, Minuit said:

I know this probably isn't your problem, but a few years ago I bought a set of those and had two of four be severely out of round.

Wouldn't that have a weird jiggle at all speeds? The Jeep is actually INSANELY smooth of a ride since I got it lifted. And it go's straight without trying to pull to either side.

[Eagle]

1 minute ago, Knucklehead97 said:

They're Cooper AT3's so not cheap Walmart tires at all  I'm going to check the tightness of everything today and will probably order new tie rod ends. The one that was spinning is the long solid one that connects to the drag link down close to the passenger side tire. I did get it tightened down enough, but feared it was shot anyways. I forgot to add that a year ago when I put the Jeep under the knife to be lifted and fix the brakes (master cylinder blew so I went with a WJ set up) the Jeep did have full on death wobble at 45-55 MPH. I drove it like this for about 30 miles and I feared the wobble destroyed a few steering parts.

 

You drove it for 30 miles with death wobble? I respectfully submit that I do not think you had death wobble. I have had death wobble. Once would be enough for anyone, and there is NO WAY I could have driven for 30 miles with what I had. There was no way I could have driven ONE mile. I was, literally, scared to death. It was all I could do to keep it on the road long enough to slow down to under 5 MPH to end the death wobble. After that, until I got it home and swapped tires, I kept it under 40 or 45 MPH.

[Minuit]

Just now, Knucklehead97 said:

Wouldn't that have a weird jiggle at all speeds? The Jeep is actually INSANELY smooth of a ride since I got it lifted. And it go's straight without trying to pull to either side.

 

I would describe my experience as the exact opposite of "insanely smooth" at any speed. Above 55 it felt like I was driving a paint shaker. Sounded about like one too.

[Knucklehead97]

1 minute ago, Eagle said:

 

You drove it for 30 miles with death wobble? I respectfully submit that I do not think you had death wobble. I have had death wobble. Once would be enough for anyone, and there is NO WAY I could have driven for 30 miles with what I had. There was no way I could have driven ONE mile. I was, literally, scared to death. It was all I could do to keep it on the road long enough to slow down to under 5 MPH to end the death wobble. After that, until I got it home and swapped tires, I kept it under 40 or 45 MPH.

By drove with it I mean I kept under 40-45 for most of the distance but often got too close to that speed and had to slow down to a near stop to keep it from shaking me off the road.

[HOrnbrod]

Have someone turn the steering wheel slightly left and right w/o the wheels turning while you're under there looking for play at every joint on the track bar, tie rod, drag link, and each front wheel. You'll probably see one TRE joint  in particular the will stand out. Then jack up each wheel separately at the frame and have someone wiggle each wheel up/down and left right while you look for play at the same spots. I think the problem area(s) will be obvious.

[Eagle]

8 hours ago, HOrnbrod said:

 

 

If there was no wobble for months then suddenly started, it's not tire balance unless a ton of weight fell off at once. Or you have square Walmart Goodyear tires installed. 

 

A TRE spinning is not normal. I've never had one. Fix/replace this first. Then check the others too.

 

But ...

 

Quote

Brand new tires balanced when they were mounted. Set toe in and caster angle myself per the instructions I was given on here.

 

If he's been driving on these tires for several months, they're not brand new. If the tires are brand new, then my comments about tire balance apply. Also, was the alignment done at the same time the tires were installed?

 

Basically, Knucklehead, you have been driving with no problems for several months. Now you have death wobble. What changed recently? That's where to start looking. When was the alignment done? Several months ago, or just a short time before the death wobble made its appearance?

 

Death wobble is a complex issue. After all the years Jeep was making solid axle vehicles, you'd think they had it figured out. But ... when the 1999 WJ Grand Cherokee came out, it had a problem with death wobble. The problem only affected the European models, with export suspension. The difference between the Euro vehicles and the American vehicles was the durometer (hardness) of the rubber bushings in the front suspension. (I assume this referred to the upper and lower control arms.)

 

One of the usual "causes" cited for death wobble is loose joints, including the track bar. But with my original '88 XJ, the original track bar eventually got so sloppy that I had nearly a quarter turn of "slop" at the steering wheel. It was winter here in New England, we had a lot of snow that year, and I didn't have an indoor garage to work in. So I drove it like that for a period of several months. I experienced no death wobble. So I don't accept that loose joints "cause" death wobble. They probably make it more exciting if it happens, but they don't cause it. Death wobble occurs when an imbalance in one front wheel is transmitted to the other front wheel, and the other front wheel then begins to wobble/shimmy at the same frequency. With both wheels wobbling at the same frequency, they enter into a harmonic where each wobble of one wheel amplifies the wobble in the opposing wheel. That's what death wobble is, and that's what differentiates it from simple wheel shimmy that's not reflected at the opposing wheel.

 

Sloppy TREs don't transmit wobble from one wheel to the other. In fact, they would tend to allow a certain amount of wobble to occur before reaching an amplitude that would transmit back through the steering linkage. An automotive tire/wheel assembly is a gyroscope. If it's properly balanced, it should be very difficult to make it wobble, and the faster it spins the more difficult it becomes to make it wobble. For that reason alone I always look first to wheel balance as being the underlying cause of any death wobble incident. Other things, sich as worn steering components, may contribute by allowing it to escalate, but they aren't the cause.

 

What were the alignment specs? Caster angle is crucial because caster helps resist/dampen wheel wobble -- did you set caster angle? If so, what did you set it to? If not -- what is it?

[HOrnbrod]

Since I discovered the Hunter Road Force tire balancer machine back in the mid-ninety's, I've never had a problem with unbalanced tires since. The Hunter balancers are completely idiot proof; even a deck ape can do it. First thing I do when I need balancing and I'm not near my favorite local shop, I ask what wheel balancer they use. If it ain't a Hunter Road Force, I'm gone.

[omega_rugal]

so, in a nutchell: anything loose in a front solid axle will result in some degree of death wooble...

[Knucklehead97]

My caster is set to 6* positive on both sides and toe in is 1/8". These adjustments were made before I got the new tires on. They were set after I replaced my suspension. I drove about 40 miles on my old tires with the new suspension and have only driven about 500 miles on the "new" tires. I installed the new tires about a week after I finished the suspension and ect. Nothing has changed recently. I haven't touched the suspension since then. I wish I could find a Hunter balancer around here but no tire shop has even heard of one.

[Eagle]

2 hours ago, omega_rugal said:

so, in a nutchell: anything loose in a front solid axle will result in some degree of death wooble...

 

No. As proven by my driving my '88 XJ all winter with a VERY loose track bar and zero death wobble.

[Eagle]

3 hours ago, HOrnbrod said:

Since I discovered the Hunter Road Force tire balancer machine back in the mid-ninety's, I've never had a problem with unbalanced tires since. The Hunter balancers are completely idiot proof; even a deck ape can do it. First thing I do when I need balancing and I'm not near my favorite local shop, I ask what wheel balancer they use. If it ain't a Hunter Road Force, I'm gone.

 

10-4. My buddy at the VW shop uses a Hunter Road Force machine.

[Eagle]

40 minutes ago, Knucklehead97 said:

My caster is set to 6* positive on both sides and toe in is 1/8".

 

 

Factory spec for caster is +7 to +8 degrees, but 6 may be the best you can do with a lift because of U-joint angles. I'd say it's marginal.

 

Factory spec for toe is zero, plus-or-minus 1/32 for each side, so it shouldn't be more than 1/16 toe-in. But I don't think 1/8" of toe-in would be enough to create any problems other than a bit of premature wear on the outer shoulders of the tires.