Death Wobble Without Stabilizer

ChattVol

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My pitman arm nut itself was tight, but the drag end has some slop. Have you had someone turn the wheel back and forth while you sit under the Jeep and analyze the track bar ends/drag link ends/tie rod ends/ball joints?

Any of those can be just loose enough or worn enough to allow some shimmy into the system when going over a pothole.
Are you running 39s on a stock sport front axle? That's a big tire on stock steering components even for mall crawling.





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WhiteJLUS

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Are you running 39s on a stock sport front axle? That's a big tire on stock steering components even for mall crawling.
LMAO no. I appreciate your concern. I made this account back when I had a Sahara and never bothered to change the name.
 

jroever

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My pitman arm nut itself was tight, but the drag end has some slop. Have you had someone turn the wheel back and forth while you sit under the Jeep and analyze the track bar ends/drag link ends/tie rod ends/ball joints?

Any of those can be just loose enough or worn enough to allow some shimmy into the system when going over a pothole.
Did that before and all joints, bolts etc. are solid. Even tried filming it during DW but camera turned off before I got to the good stuff. But there is a clicking sound when steering turns past center that makes me wonder. Will remove synergy brace and put the old pitman arm nut back on. If the clicking continues I'll see if I can have the steering box replaced under warranty ...

TxJeepers, any luck with the steering box replacement yet?
 

jroever

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I had an interesting conversation with one of the techs at MC - he pointed out that since JLs have an electro/hydraulic power steering system there is a torque sensor somewhere that will likely get different readings if the steering stabilizer is removed. That means that if the SS is removed the power steering could become a contributing factor in DW!
This made me wonder how the Synergy sector shaft brace in combination with the aluminum steering gearbox would be affected by this. Steering would be tighter but if there is a sensor inside the gearbox and we just changed the way the steering bore tilts (reinforced at bottom but not at top / inside gear box) this could cause stronger readings at the sensor and could cause the power steering to potentially amplify the wobble! Just a theory - but in my case DW started when I added the sector shaft brace and potentially mounted the original SS upside down (following the labels on the shock with relocation kit can result in the shock upside down - you will need to make sure the flow channel that was added recently is at the bottom, not at the top or the side!).
When I removed the brace and added SS with correct orientation my DW is mostly gone (and yes steering has more slop again). I was able to get a sustained wobble once but it was not the death type that increases in amplitude. I do know that I have an s-load of balancing weights on my 37" patagonias and the alu gearbox to still explain that.
So I am hopeful that getting the steel gearbox and a better SS might be the solution for me.
Given that the steering stabilizer might now be a meaningful component in the steering feedback loop for JLs (which was not the case for JKs!) I can now also easily justify to add a Fox TS stabilizer... but one step at a time!

PS: Don't get me wrong - I love my track bar/sector shaft brace - I just won't put them back on until I have the TSB for the steering gearbox done!
 

rrsontag

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So I removed my trackbar brace because why not at this point. Paying attention to the amount of clamping force on the trackbar before and after. It does seem to me that the trackbar is clamped tighter without the brace. Now I didn't measure or anything just the eyeball test, so take it with a grain of salt.

Also took the jeep back to Discount for another round of road force balancing. I noticed the spare has an impressive amount of weights on it. This lead me to asking why there are so many weights. They just said they had a hard time balancing some of the tires. But ultimately got them.

Now I feel like there is an improvement, (could be psychological), but I don't feel as much shimmy.

So is balancing solely to do with the tires or do the wheels play a factor as well? I assume they would have to on some level. Then if they are that difficult to balance, after riding in one spot for several thousand miles, would a rotation cause issues? Do we have to rebalance after every rotation?
 

WhiteJLUS

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So I removed my trackbar brace because why not at this point. Paying attention to the amount of clamping force on the trackbar before and after. It does seem to me that the trackbar is clamped tighter without the brace. Now I didn't measure or anything just the eyeball test, so take it with a grain of salt.

Also took the jeep back to Discount for another round of road force balancing. I noticed the spare has an impressive amount of weights on it. This lead me to asking why there are so many weights. They just said they had a hard time balancing some of the tires. But ultimately got them.

Now I feel like there is an improvement, (could be psychological), but I don't feel as much shimmy.

So is balancing solely to do with the tires or do the wheels play a factor as well? I assume they would have to on some level. Then if they are that difficult to balance, after riding in one spot for several thousand miles, would a rotation cause issues? Do we have to rebalance after every rotation?
Wheels can definitely play a part, and a rotation can cause issues depending on whether or not you had any kind of uneven tire wear on the tire where it was sitting prior.

Your tires shouldn't really need re-balancing with every rotation, provided that your alignment is good, and stays good.
 

Jeep&dogs

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I had an interesting conversation with one of the techs at MC - he pointed out that since JLs have an electro/hydraulic power steering system there is a torque sensor somewhere that will likely get different readings if the steering stabilizer is removed. That means that if the SS is removed the power steering could become a contributing factor in DW!
This made me wonder how the Synergy sector shaft brace in combination with the aluminum steering gearbox would be affected by this. Steering would be tighter but if there is a sensor inside the gearbox and we just changed the way the steering bore tilts (reinforced at bottom but not at top / inside gear box) this could cause stronger readings at the sensor and could cause the power steering to potentially amplify the wobble! Just a theory - but in my case DW started when I added the sector shaft brace and potentially mounted the original SS upside down (following the labels on the shock with relocation kit can result in the shock upside down - you will need to make sure the flow channel that was added recently is at the bottom, not at the top or the side!).
When I removed the brace and added SS with correct orientation my DW is mostly gone (and yes steering has more slop again). I was able to get a sustained wobble once but it was not the death type that increases in amplitude. I do know that I have an s-load of balancing weights on my 37" patagonias and the alu gearbox to still explain that.
So I am hopeful that getting the steel gearbox and a better SS might be the solution for me.
Given that the steering stabilizer might now be a meaningful component in the steering feedback loop for JLs (which was not the case for JKs!) I can now also easily justify to add a Fox TS stabilizer... but one step at a time!

PS: Don't get me wrong - I love my track bar/sector shaft brace - I just won't put them back on until I have the TSB for the steering gearbox done!
I have actually had a pretty extensive conversation with one of the FCA electronic engineers on what impact the computer has on the power steering. He said it’s simply not true that the computer controls anything with the steering other than increasing or decreasing pressure based on RPM just like a belt driven pump. All the software changes they have done simply increase the ramp up of the assist or change the overall pressure over the entire range.
 

jroever

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I have actually had a pretty extensive conversation with one of the FCA electronic engineers on what impact the computer has on the power steering. He said it’s simply not true that the computer controls anything with the steering other than increasing or decreasing pressure based on RPM just like a belt driven pump. All the software changes they have done simply increase the ramp up of the assist or change the overall pressure over the entire range.
As I said - just a theory - and to better understand the topic I brushed up my understanding by watching this Video from 1956! So I get it now that there is no electronic torque sensor - but there is a mechanical control valve that is actuated by the movement of the cam shaft. This works both by input from the steering wheel or feedback from bump-steer which should result in a stabilizing counter pressure.
So if the aluminum gearbox flexes, that could cause all kinds of unwanted effects on this feedback mechanism (same theory as before, but now completely mechanical based).
And to bring the electro/hydraulic pump and stabilizer back into the picture (after all FCA engineers did redesign it) - I would think removing the SS from the system will end up triggering the dampening attribute of power steering more often - so the pump should be more active than without SS removed ... add a bit of hysteresis into the electro/hydraulic pressure regulation system and things might no longer behave like good old JKs did ...

I know the steering gearbox TSB specifically states that "sustained steering shake, shimmy or vibrations" will not be fixed by this - but I would really like this to be wrong
 

jroever

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Just to report back here - had the steering TSB done. Death wobble is gone!
The car does not drive straight as long as it did before when if I take my hands off (either left or right), but the steering is much tighter now and the pot hole I used to trigger DW in 2 out of 3 attempts is now 0 out of 5! I am happy as a lark!

@Jeep&dogs: even with electric RPM based control vs belt, if the electric is able to create more pressure during low RPM that could be enough to create a much stronger correctional force during hitting a bump at low speeds. Enough to create a resonance case that a) does not exist with belt driven systems, b) could highly depend on the gear-box design and setup and c) would need to have a steering stabilizer in the loop to avoid.

I agree with all other established JK wisdom that SS will not fix a death wobble due to classic case of loose joints, bad alignment etc. - but even with perfect alignment and joints, MY JL needed the gearbox and SS to fix my DW.

Dealership did not perform an alignment after the gear-box change even it is mentioned in the TSB. They claimed they don't have the equipment and therefor only did a test-drive. Sigh. They banged up my pitman arm quite a bit - hope that was not while attached to the new gear-box! And it makes me question the mechanics ability to use the proper tools a bit.

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As far as I can tell there was no software update done either - but my JLUR is a 2020 so it might not have needed it.

I still have to put the track bar and sector shaft brace back on. Curious if it will even make a difference with the iron gear-box from a steering feel perspective.

PS: when I first picked up the car after the TSB the steering wheel felt a bit harder to turn - but now after a while it feels ok. Could have been maybe some air in the hydraulics or maybe I got used to it.
 

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