Death wobble after 2.5” Lift on 392 ! SOLVED !

[Roxanne68]

It doesn’t seem to like my videos, so here is a pic of the sophisticated measurement set up (paper ruler and zip tie). I probably could have just used a dial indicator, but where is the fun in that.

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[J.Ferreira]

Have you tried driving since you put on the new track bar?
Should have helped pull everything back into alignment.

 

[J.Ferreira]

It doesn’t seem to like my videos, so here is a pic of the sophisticated measurement set up (paper ruler and zip tie). I probably could have just used a dial indicator, but where is the fun in that.

The videos loaded just fine. lol

 

[Roxanne68]

Have you tried driving since you put on the new track bar?
Should have helped pull everything back into alignment.

Clayton track bar arrives Friday, still on the stock one till then

 

[J.Ferreira]

Clayton track bar arrives Friday, still on the stock one till then

For some reason I read, "get them installed later tonight" not later this week lol
I think it'll help a lot, right now your stock track bar is pulling the axle to the drivers side, IIRC. That's not helpful as far as driving straight and true, of course.

 

[word302]

Ok few things here. 1/4” toe is A LOT. I’d lower it to 1/16”-1/8” total toe. 150’lbs on those jam nuts is not enough. Use a paint pen to be doubly sure they aren’t moving. ANY amount of movement in the track bar will cause all kinds of havoc when you hit bumps. Like someone else said the factory track bar is garbage and the factory mount is suspect at best. Once you start lifting you increase leverage on all those mounting points. I think you’re on the right track, ball joints should be high on your list of mods as well. We’ve seen the factory BJs last as little as 5k miles, especially with bigger tires.

 

[J.Ferreira]

Ok few things here. 1/4” toe is A LOT. I’d lower it to 1/16”-1/8” total toe. 150’lbs on those jam nuts is not enough. Use a paint pen to be doubly sure they aren’t moving. ANY amount of movement in the track bar will cause all kinds of havoc when you hit bumps.

I didn't think that was possibly what he meant. lol That is a fuck ton of tow.

 

[word302]

I didn't think that was possibly what he meant. lol That is a fuck ton of tow.

Yeah I’m guessing that’s a big part of the issue here.

 

[Roxanne68]

To be fair, It’s a hair under 1/4” total toe, but it was in the factory tolerance so I left it. But as you pointed out, I really should get it to under 1/8”. It never so much a shimmy’ed on the same railroad crossing that it can’t make it over now without DW. All at the same toe in.

my plan is to touch nothing, I will toss in the new TB and see what it measures for movement and take it to my test road to see how it performs with the set up as is. If that brings it back, I will dial in lower toe, and install the new drag and tie rod. Like to do one thing at a time to confirm the impact.

ball joints should be high on your list of mods as well

They are on my list for this winter

thanks everyone for the input so far, appreciate it.

I told myself I would not mod this one too much, slippery slope… Mission is failing.

 

[word302]

To be fair, It’s a hair under 1/4” total toe, but it was in the factory tolerance so I left it. But as you pointed out, I really should get it to under 1/8”. It never so much a shimmy’ed on the same railroad crossing that it can’t make it over now without DW. All at the same toe in.

my plan is to touch nothing, I will toss in the new TB and see what it measures for movement and take it to my test road to see how it performs with the set up as is. If that brings it back, I will dial in lower toe, and install the new drag and tie rod. Like to do one thing at a time to confirm the impact.



They are on my list for this winter

thanks everyone for the input so far, appreciate it.

I told myself I would not mod this one too much, slippery slope… Mission is failing.

I don’t know how many times I’ve told my wife my mods were almost complete. I’m careful not to leave the Dakota Customs hemi conversion page open?

 

[Roxanne68]

Well, did the next preventive measure, adjusting toe. I pulled out the better tools to get more accurate measure:

• Before: 3/16” total
• After: 3/32 (or as close to that as you can get with tape measures)

Took it for a drive, no change. Can induce a very heavy wobble at 30mph and a deep manhole cover. Didn’t expect a cure, but was hoping for a noticeable reduction in the pre DW, but not to be.

2nd: tires. Didn’t have them re balanced, but, did rotate. No change. All the weights are in place, tires only have 8000 miles on them, tread is very even, and it is glass smooth up to 90, don’t think they are an issue. PSI was at 33.

next up:

• Currie drag link. Like alignment, not expecting much, but the pinion side rod end is a little loose on the stock one so it’s due, and may help sharpen steering a bit.
• Clayton track bar. Want to do this next, but fedex had a major system IT issue and the package was delayed so it will have to wait til after drag link. Banking on this change, if not, about all that’s left is ball joints.
• Once the wobble is under control, will probably swap out the SS since the stock one has a few miles on it, and get a little stiffer damping. Mostly just for a little firmer steering and some DW insurance.

 

[Roxanne68]

Success!

installed the Currie drag link, as expected, didn’t really make any noticeable difference in propensity to wobble. It did seem to make the steering a touch more responsive. Frankly the stock one was in good shape.

The Clayton track bar did the trick. Centered the axle and installed with grade 8 9/16-18 hardware torqued to 156 ftlbs. It reduced the lateral movement of the axle relative to the chassis to less than 1/16”. Turn in response on the road was noticeably improved as was tendency to wander with minor changes in the road surface.. I drove to my 2 spots where I can reproduce DW at will and hit them at full speed. The one obstacle resulted in only a minor shimmy and the other didn’t even wiggle the steering wheel. I would say better then when the Jeep was stock Very happy.

Looks like it was the stock track bar that was not capable of controlling the Clayton springs/fox 2.5’s. I think I will toss on stiffer steering damper just to eliminate the shimmy and give a bit of margin.

Thanks to everyone who gave input, appreciated the help!

 

[roaniecowpony]

Success!

installed the Currie drag link, as expected, didn’t really make any noticeable difference in propensity to wobble. It did seem to make the steering a touch more responsive. Frankly the stock one was in good shape.

The Clayton track bar did the trick. Centered the axle and installed with grade 8 9/16-18 hardware torqued to 156 ftlbs. It reduced the lateral movement of the axle relative to the chassis to less than 1/16”. Turn in response on the road was noticeably improved as was tendency to wander with minor changes in the road surface.. I drove to my 2 spots where I can reproduce DW at will and hit them at full speed. The one obstacle resulted in only a minor shimmy and the other didn’t even wiggle the steering wheel. I would say better then when the Jeep was stock Very happy.

Looks like it was the stock track bar that was not capable of controlling the Clayton springs/fox 2.5’s. I think I will toss on stiffer steering damper just to eliminate the shimmy and give a bit of margin.

Thanks to everyone who gave input, appreciated the help!

Once you go through this and learn the cure, you can really get right to the cause of steering issues later. These JLs are a finicky steering bunch.

 

[Roxanne68]

Once you go through this and learn the cure, you can really get right to the cause of steering issues later. These JLs are a finicky steering bunch.

Yeah, I tend to agree. I also suspect that there are number factors converging which tend to magnify theses steering issues:

• Average vehicle speeds are up over the years (I drive my Jeep more like a sport sedan, never did that in my cj because it couldn’t)
• Increase in vehicle weights putting greater demand on chassis and effecting natural resonance frequency of the system
• People’s expectations around drivability/comfort have increased over the years driving design changes to enhance these elements at the expense of other performance criteria.
• Higher lifts and bigger tires then 10 years ago contribute

all of these things and more are narrowing the operating range of the system. Yes all solid axles are susceptible to shimmy and DW, but some designs are much more prone to it than others.
in my case, the parts I replaced to fix were not really out of spec, just not capable of managing the changes that were made.

And on the topic of stabilizers, I don’t quite susbscibe to conventional wisdom that they are just a bandaid. Even if all complements are in spec, All solid axle front ends can be stimulated into DW under the right conditions, it’s just that most systems are operated in a range where they don’t have issues. Unfortunately the JL operating range appears to be fairly narrow, and even minor degradation in parts will push it over the edge (degradations which may not even bother other vehicles). The stabilizer gives it a larger operating range in the real world. This is the norm in the performance motorcycle world, trade off for turn in performance is stability and stabilizers are required (yes even on the street, and as scary as DW can be to some, head shake on a bike at 100mph is orders of magnitude more frightening). A blanket statement that they are not needed is not entirely factual or practical for some chassis designs. Nor should they be used to mask components that are out of specification and due for replacement either.
Just some ramblings, YMMV

cheers

 

[Fast-n-Furious]

@Roxanne68 I’m very glad you went through all the diagnosis and the Clayton track bar made the fix. I’m looking for the track bar upgrade mainly to center the axle after installing Clayton coils. 1/4” shift to the drive side, doesn’t bother me much but I wanted to improve the steering feel.

Do you still like the Clayton track bar? I’m also comparing it with other brands, wanted to hear your feedback.

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