Death Wobble: A 21 month saga. FIXED!

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

The frame is most definitely flexing. The motion of the track bar bracket is there. There may even be motion between the track bar brace and the track bar bracket as well which is really annoying since the brace is both bolted and welded on both ends. In the second video you can definitely see motion between the TB brace and passenger side frame rail forward of the brace. The frame as mentioned earlier is plated in 3/16ths with plenty of rosette and skip welds (plate photo's earlier in post). If there are cracks they are under that plating. I hope that I just have some broken welds between the TB bracket and the frame plating. Now some of that motion in the camera is the forward part of the frame horn moving which moves the camera. The steering box and track bar fight each other bending the frame rail (I have NO bumper or anything else) tying the front end of the frame horns together right now.

A 220V welder and new welds on the TB bracket along with a new joint on the TB frame end are soon to happen.

John

 

[rockclimber]

Re: Death Wobble: An 18 month saga. Need help still

that bracket is moving a lot on the frame.

I would see what a new joint does.


but you have had bad enough death wobble for a while now, I would strip both unirails down to bare metal and look for cracks. then I would plate and fully weld all the way around.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

that bracket is moving a lot on the frame.

I would see what a new joint does.


but you have had bad enough death wobble for a while now, I would strip both unirails down to bare metal and look for cracks. then I would plate and fully weld all the way around.

The new joint will be here tomorrow. Stripping the existing plating off of the frame rails is not going to happen. There are a lot of rosette welds on each plate. The skip welds are easy enough to get to but the rosettes cant be cut without digging into the frame rail, in theory yes, in practice no.

I looked at additional video's (not published) taken from the passenger side. The TB brace does not appear to be moving at all which is good news. I think the TB bracket is "rotating" about the brace. There is motion between the bottom of the frame rail and bracket (broken welds) and the bracket is flexing the outside of the frame rail as the bottom of the bracket moves side to side.

The welds between the frame bottom plating and the track bar bracket are "bird crap" and are almost certainly broken. The welds between the frame side plates and the track bar bracket are good. I will cut out and re-weld the bird crap welds. If I can get the TB bracket off (should not be too hard) I will inspect the plating under it and if possible add plating to the inside of the frame rail back to the fire wall. I will also look at widening the TB bracket front to rear so It spreads the load out over more of the frame rail.

Lots to consider, lots to do. First up is the new joint.....

John

 

[rockclimber]

Death Wobble: An 18 month saga. Need help still

By bare metal, I meant no paint so you can see what you are doing not to remove stiffeners

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

OOPs my bad on understanding what you meant. I was sort of wondering how you got so unreasonable in your suggestions.....

John

 

[rockclimber]

Death Wobble: An 18 month saga. Need help still

OOPs my bad on understanding what you meant. I was sort of wondering how you got so unreasonable in your suggestions.....

John

My next suggestion will be to crush your jeep and start over.

 

[Wayne Sihler]

Re: Death Wobble: An 18 month saga. Need help still

My next suggestion will be to crush your jeep and start over.

Have you seen his Jeep ?

The "crushing " is mostly done :wave1:

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

WBSJP

As you well know my Jeep wins trophies every year in the show and shine competition.
Its a legend around these parts. It goes where JK's on 40's fear to tread.

 

[Wayne Sihler]

Re: Death Wobble: An 18 month saga. Need help still

And you are real proud of that.........party1:
Putting JK,s in their place since 07....

 

[Sardog1]

Re: Death Wobble: An 18 month saga. Need help still

I have a 2001 XJ that developed death wobble after installing a 3" lift (in 2001 so all other parts were in almost new condition). Nearly scared the shite out of me! Had it aligned twice and tires checked and rechecked for balance. Oddly, after swapping the original tires (same rims) for some MTR's, the problem went away. Went through 2 sets of MTR's and am now running Cooper Discoverer STT's without issue. Not sure if the added weight and or larger diameter (30") made the difference or just the way they grip the road did it. Any chance you could borrow someone else's tires/wheels and see if you still have DW? Hope you get it sorted out.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

Sardog1

While it is possible that tires are part of the problem I have replaced the ones I had when all this started and I also put on new rims. Now the last two sets have been used tires, about 50% tread depth so there could be a problem, but even after swapping fronts and rears it has not changed. I did swap tires with a friend who did not have DW but to no avail. I am focused on chassis flex and the movement of the track bar bracket and chassis side TB joint right now.

Update:
Its been raining here since last weekend. It stopped yesterday but honey do's dominated....

Until tonight. Ground away all the bird crap welds on the TB bracket where it attaches to the 3/16ths plates already on the bottom and outside of the frame. Only the ones on the bottom were actually crap welds (upside down with to low a setting on the welder). The plate on the bottom of the frame rail was very poorly welded to the unibody. Almost no welds around the perimeter and huge gaps between the outside vertical plate and the bottom plate.

Ran some silly heavy extension chord from the only 20 amp circuit in the house. Cranked the welder up to the reccomended setting for 3/16ths plate and started welding. Nice clean welds now join the TB bracket to frame rail bottom plate. Bottom plate is now nicely joined to the bottom of the unibody frame rail most of the way around. It was bit messy but the gaps got filled at a lower setting on the welder. Multiple passes to get it all closed up and joined to the unibody. Then I ground everything down and made another pass at high current and voltage settings (still popped the breaker a few times). Now the welds look good and are solid.

Tomorrow the new TB rod end goes in and if I have light I will get some video of it all.

John

 

[shanesaw]

Re: Death Wobble: An 18 month saga. Need help still

I have read that warped rotors can sometimes be the source of death wobble. Might be worth checking.

 

[Devilfrog]

Re: Death Wobble: An 18 month saga. Need help still

I just got rid of the last of my DW, my trac bar bracket was ... rotating on the brace. would only do it if the engine was running so under power steering input. More bracing solved that issue.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

Led a ride yesterday from the passenger seat of friends XJ. Sure want mine back. So today I took the first video after rewelding the TB bracket and some of the frame doublers along with putting in the new chassis side joint. As the short video below shows I still have DW. If you look closely during the DW the bracket is not moving and there is no motion in the rod end. Need to look elsewhere for a while. There is something that is causing the tire to start moving side to side and I dont think its related to the TB or TB bracket. This is happening on a very smooth road and comes on with speed. No bumps required.

http://www.youtube.com/watch?v=vDpjL5ghqCQ

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

I have read that warped rotors can sometimes be the source of death wobble. Might be worth checking.

No brake pedal pulsing which is a normal sign of warped rotors.

I just got rid of the last of my DW, my trac bar bracket was ... rotating on the brace. would only do it if the engine was running so under power steering input. More bracing solved that issue.

What did you do to add additional bracing?

______

Tossed in a couple extra degrees of caster but it had no affect, still have DW.

John

 

[Devilfrog]

Re: Death Wobble: An 18 month saga. Need help still

It's at the welders getting a front receiver and recovery points added, I get it back Monday-ish ... I'll snap a picture then.

It looks like the tires are starting the process .... so something knuckles out or a tire is having belt separation issues. I've fought with that one before ... they balance up fine but shake to all hell on the highway.

 

[yossarian19]

Re: Death Wobble: An 18 month saga. Need help still

Side to side can only be the track bar, right?
How does the axle side tb bolt fit in the axle bracket? Loose? Needs to be tight. Weld washers or bore bushing and bracket for oversize bolt if needed.
The factory tb hardware is specked stupid tight. Iirc almost 100 ft lbs. is you stuff tight?
I'd go 1/2" hardware if you haven't already

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

It's at the welders getting a front receiver and recovery points added, I get it back Monday-ish ... I'll snap a picture then.

It looks like the tires are starting the process .... so something knuckles out or a tire is having belt separation issues. I've fought with that one before ... they balance up fine but shake to all hell on the highway.

Pictures would be appreciated.

I will be swapping fronts and rears tonight to see what happens and I have a friend coming over later this week to do a tire swap as well. The last video sure looks like tires to me. I intentionally kept it vibrating a low rate in the second DW clip in the last video so I could look at the steering box and TB bracket to see it there was any motion there, I can see any until the whole rig starts jumping around. Makes me hopeful that it is tire related. Unit bearings and ball joints are new (last 6 months with only DW test drives on them).

Side to side can only be the track bar, right?
How does the axle side tb bolt fit in the axle bracket? Loose? Needs to be tight. Weld washers or bore bushing and bracket for oversize bolt if needed.
The factory tb hardware is specked stupid tight. Iirc almost 100 ft lbs. is you stuff tight?
I'd go 1/2" hardware if you haven't already

Bolts on both ends of the TB are 1/2 inch. Long shank on bracket end. Slip fit in the rod end. Bolt in TB bracket has just between 0.012-.015 slop (Yeah I checked it with a dial indicator). I could fab up some doublers and offset them to "clamp" the TB bracket bolt before welding. If ten thousandths of side to side motion in the axle is all it takes to kick off DW....wow. The rubber bushing on the axle end of the TB has a lot more compliance than that.

I torqued the bolt "stupid tight" 18 inch breaker bar two hands and everything I could give it. My torque wrench only goes to 150ftlbs. I will check it for fun tonight (numbers mean something, stupid tight doesnt) but I doubt I can measure it.

Tonight's fun list: Torque check and tire swap.

Keep the ideas coming. It gotta be close to solved now. Chassis is stiffer than its ever been and the parts up front are ALL new and most are upgraded.

John

 

[Devilfrog]

Re: Death Wobble: An 18 month saga. Need help still

In reality stock torque specs are 75ft-lbs at the axle and 65 at the frame.
I had set of upper bushing ground out (inner nubs removed) and used 1/2" bolts which fit as tightly as the lowers using 9/16" bolts. Removed all the slop.
In the end the real improvement cme from the 3 link long arms reduced angles and several re-aligns.

 

[nosigma]

Re: Death Wobble: An 18 month saga. Need help still

TAIL CHASE!!!!!

As I did the tire swap and while each side was up in the air I gave the tires a light shaking top-bottom (camber) and front-rear (toe). As soon as I shook the front right I could feel it. Then I could hear it. A light thumping noise from the drivers side.

Lifted the drivers side and shook it. Very light thumping and very little motion top-bottom (camber) but a whole lot (about 1/8 inch) in the toe direction. Sounded like wheel bearing. Had my wife come out and shake the tire while I felt around (the suspension) and listened. No doubt. Wheel bearing. I could feel the "shock" from steering box to the passenger side tire getting stronger all the way there. Put my hand between the brake caliper and rim, very obvious motion there as well as down inside where the axle passes through the bearing.

I had replaced this about 6 months ago and probably beat it to death while I chased down the bigger issues as well as the other "tail chase" parts.

Off to get a new unit bearing......tire tests and torque check in a day or two.

Not fixed yet but its getting closer!!!!!

Devilfrog:
I did EXACTLY the same thing about two years to my axle end rubber bushings, bored them out lowers and uppers (uppers are a bit smaller) and then I honed the bores on the Rustys high misalignment joint at the chassis and. Went to bigger SAE course there grade 8's. Had to open up the chassis side but that took care of the hammered out holes at the attachment points. Every thing is slip fit and the improvement was very apparent. Havent had any damage to the holes since then. Still as tight as the day I did it.

John