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Unread 05-14-2015, 12:32 PM   #1
mrblaine
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Death Wobble from lifted motor

How many have experienced this?

Good or reasonably good front end components, do nothing to the suspension or trackbars and just do a MML with stock or similar mounts and blocks under them?

Then on the test drive, a severe shimmy, wobble, or even full blown DW shows up for some seemingly unrelated reason?

If so, post up and I will tell you of at least one solution I've found and tested after a lot of point by point A/B comparison of one component at a time.

This includes the following
new tires does it before and after
new Currie Trackbar and that includes swapping the axle side bushing with less than 5000 miles on it for a new one, no change
Adjust JJ races with a shim to tighten them up.
Near new Currie steering with no play
No play in steering gear or steering shaft u-joints and in fact it is one of the tightest ZJ gears I've ever seen.
Stock Pitman arm.
New Currie control arms, now new Savvy control arms including JJ conversion at axle.
Rubicon rims which are very true and high quality and I've checked them for run-out and wobble both ways.
33" tires no cupping, no tread hop, no squirm
No cracks or other apparent weaknesses in frame including the mount for the steering gear.
Several different stabilizers just to see the effects each had. None mattered
Toe is correct
Caster is correct (doesn't matter, just listing the known goods)
Vehicle is sub 60,000 miles, no rust
Unitbearings are new, and it also did it with low mileage OEM
Knuckles and balljoints are new and sound, also did it with OEM knuckles and balljoints.
Axle shafts and u-joints are new and it has done it no matter which of the 4 sets of shafts have been in it.
2nd newish front axle to be under the rig, symptoms did not change with either axle.
Vehicle has had 3 different brake kits on it, symptoms did not change.
Same MML, Same BL, stock t-case belly skid. No vibes while driving at any speed from drivetrain. Driveshafts are known good and balanced.
Rear is the second D-44 I've had under it, symptoms didn't change with either one.

There is only one commonality across the board other than it doesn't show up with new perfectly round and balanced tires, only after they get a couple of thousand on them and some tread wear, but no cupping, no shimmy at all.

It has had 1 set of 35's, 1 set of OEM tires and 2 sets of 33" tires, only the OEM ones didn't wobble and we stay on top of tire balance.

Any guesses or questions?

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Unread 05-14-2015, 12:38 PM   #2
ravenworks
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This sounds like a nightmare to throw time & money at.
I was thinking just yesterday in a thread across the street,"Why, I do this to myself"?
For the most part I have been fortunate to have you guy's.
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Unread 05-14-2015, 12:56 PM   #3
bbradUSMC
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When I did my MML with Brown Dog 1" mounts this happen to me. New TRE's and SS helped. I was running stock steering, BFG 33" all terrains and 4" pro comp lift. However, I swapped out my tires to Good Year MTR kevlars and right away had a shimmy that escalated to DW. I fixed the death wobble when I installed my MC lift (control arms, track bars, currie 4" springs) and had a new TB mount welded to the frame. I still have a shimmy that only gets better after I rotate my tires and get them balanced. I recently installed the crown HD kit but have not had many miles on it because my pinion bearing is bad in the front. Going to pull the front shaft and drive it this weekend. I have new ball joints, unit bearings, lopro trans mount w/ UCF ultra high skid, rebuilt front shaft and TW rear shaft. Never even occurred to me that the MML could be the cause of a shimmy or DW.
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Unread 05-14-2015, 03:44 PM   #4
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Trans mount? Mine got kinda bound up after the MML, a few washers as spacers between the mount and skid on the forward 2 bolts seemed to help, changing it for a new one didn't.
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Unread 05-14-2015, 05:48 PM   #5
EricsGreen98Tj
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I think this is what started my DW adventure. With stock everything there was not shimmy/DW. After installing a 1.25"BL/ 1" Brown Dog MML I'd have DW but it only came around when taking a significant turn between 45-50 mph.

After 3" lift plus front upper and lowers, JJ housing kit, adj trac bar, and Zj steering, plus new 35s I haven't had any DW at all.

I also replaced the Brown Dog MML with some cheap eGay 1" MML steel pucks and OEM mounts. But this was done because of the vibe transmitted during idle.

So did the cheap MML fix my DW, or did all the new parts in the front end?
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Unread 05-14-2015, 08:04 PM   #6
joe_jeep
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I got a similar issue, But im pretty sure mine it related to junk tires, and too much backspace.

I did all currie arms, currie track bar, currie jj housing kit,
Used re 3.5 springs(that netted 3.5" lift exactly),
Currie poly 1" motor mounts, prothane poly trans mount, energy susp 1" poly bl.
Was totally stock b4 all this, drove perfect. Its never been off road.

I put on a free set of used up 33s, on new 17" rims with spacers. 3.5" back space total.
Drove it, had a shimmy.

Replaced all the steering with all zj stuff. Every part, but had no steering stabilizer on it.
then had full blown dw!

added a new monroe sc2928 stabilizer, no dw, but its close.
u can feel it trying to dw. Still has a shimmy bout 45 ish.

getting new 35s and stock tj aluminum rims asap.
get back to around 4.25 to 4.0 back space.

I will do all the ball joints and wheel bearings too, they feel tight, but got hi miles.
thats about the last front end parts I have not changed at 100k miles.
and a real alignment. Got a feeling I got very low caster.

if u were close, I would be dropping it off to get it done right.
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Unread 05-14-2015, 08:35 PM   #7
mrblaine
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Quote:
Originally Posted by joe_jeep View Post
I got a similar issue, But im pretty sure mine it related to junk tires, and too much backspace.

I did all currie arms, currie track bar, currie jj housing kit,
Used re 3.5 springs(that netted 3.5" lift exactly),
Currie poly 1" motor mounts, prothane poly trans mount, energy susp 1" poly bl.
Was totally stock b4 all this, drove perfect. Its never been off road.

I put on a free set of used up 33s, on new 17" rims with spacers. 3.5" back space total.
Drove it, had a shimmy.

Replaced all the steering with all zj stuff. Every part, but had no steering stabilizer on it.
then had full blown dw!

added a new monroe sc2928 stabilizer, no dw, but its close.
u can feel it trying to dw. Still has a shimmy bout 45 ish.

getting new 35s and stock tj aluminum rims asap.
get back to around 4.25 to 4.0 back space.

I will do all the ball joints and wheel bearings too, they feel tight, but got hi miles.
thats about the last front end parts I have not changed at 100k miles.
and a real alignment. Got a feeling I got very low caster.

if u were close, I would be dropping it off to get it done right.

Before you change anything like tires, I have a very simple solution that will add some more data to the DW file if you're of a mind to do a small bit of work. It's fairly cheap, takes about an hour and will at least eliminate one possibility out of the equation.

After I've gone over this rig with a very critical eye only to find nothing, I finally put 2 and 2 together after a little brain tickle helped me remember the posts I've read about MML causing issues. I spent some time pondering WHY that would create it and the only thing I could come up with was a change in the stiffness of the frame in that area.

So, I made a small brace and ran it from the back side of the track bar mount over to the opposite frame rail right under the harmonic balancer.

These braces are not new to me. I made many of them to help with steering stuff and to keep our track bar mounts attached before we all switched over to hydro-assist.

I use the small right and left hand threaded clevis they use for limit straps with 1/2-20 threads and tube adapters into .085 7/8" tube. Couple of 1/4" tabs on the frame and mount, turn the tube to add a bit of tension and tighten it down.

Not exactly super cheap, not expensive and for the problem I solved on this one, fairly priceless.
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Unread 05-14-2015, 08:44 PM   #8
joe_jeep
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So basically your adding tension the track bar mount?
You think the track bar mount itself is flexing.
I have thought about beefing up the mount, its not exactly beef.
I stiffened up pretty much everything with all the poly, and beef suspension parts.
Pretty strong bumpers at both ends limiting frame flex some too.
I can see how that would change things. Moving flex from one point to another.

Do u have any pics of what u did?
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Unread 05-14-2015, 08:44 PM   #9
mrblaine
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Quote:
Originally Posted by ravenworks View Post
This sounds like a nightmare to throw time & money at.
Not at all. I don't mind adding to my knowledge. For the most part, all the new parts have been part of some project I was using the vehicle for anyway so no harm there.

When I put a new axle under Kat's, I took the HP 30 I had polished and put it under this one because I had a matching rear axle with the same gears out of a Rubicon complete with factory locker.

I got the double adjustable Savvy arms so I could mess with the tension on the upper JJ's and see if that made any changes without pulling one end and I prefer them anyway.

The lift kit was a good thing to do to learn about the Savvy 3" kit so I don't mind that and it is just about right for 33's.

When this first started, I suspected the factory bushings in the original axle and since it only did it at 65 mph in slight turns on the freeway with no other symptoms, I lived with it until I could find some time to play with teaching myself some more about DW.

I can diagnose the root cause of most normal DW cases in person in just a few minutes so having one like this that I actually owned was pretty special.

For the record though, if you went for a ride with my helper and experienced what he had to do to make the wobble show up, you'd make him pull over and beat him senseless with a hi-lift jack handle.
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Unread 05-14-2015, 09:02 PM   #10
mrblaine
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Quote:
Originally Posted by joe_jeep View Post
So basically your adding tension the track bar mount?
Yes, but it could be either tension or compression or even none if you just want to put bolt tabs on the end of the tube.
Quote:
You think the track bar mount itself is flexing.
No, not the mount. I believe that the mount is twisting the frame along it's axis.
Quote:
I have thought about beefing up the mount, its not exactly beef.
I stiffened up pretty much everything with all the poly, and beef suspension parts.
Pretty strong bumpers at both ends limiting frame flex some too.
I can see how that would change things. Moving flex from one point to another.
The mount is fine it doesn't need anything and it has plenty of weld attaching it to the frame so that isn't going to fail either or even flex. It has to be the frame twisting due to how low the mount is and then the MML allows a longer lever to work against the rubber in the OEM mounts.

The Motor Mounts are basically an additional cross member to tie the sides of the frame together through the engine block. I suspect when we raise the motor, we increase the flexibility or at least change it in some way that allows the track bar mount to cause problems in stability.

Quote:
Do u have any pics of what u did?
There are a few floating around of the ones I've done before but I'll get some of this one.
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Unread 05-14-2015, 09:51 PM   #11
ravenworks
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Quote:
Originally Posted by mrblaine View Post
For the record though, if you went for a ride with my helper and experienced what he had to do to make the wobble show up, you'd make him pull over and beat him senseless with a hi-lift jack handle.
I would have to borrow one since I don't own one,unless I used his.
OK,I thought about this and it make perfect sense.
Now you have me wondering if you could use a saddle that would come down under the oil pan with plates on each end to tie it into the MM,this could also serve as a mounting point for a skid.
Is that what you did?
Another question comes to mind,don't we want some radial twist so other things don't break?
I guess what I am getting at is, I could make it to rigid therefore introducing another/other set of problem(s)
Edit: I think I am seeing what you did now.
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Unread 05-14-2015, 10:07 PM   #12
bbradUSMC
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That is very interesting Blaine as I removed one of the "frame supports" from my jeep when I got it and soon after installed the Brown Dog 1" MML. It came with the pro comp kit that was originally installed. Maybe I shouldnt have taken that off haha.
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Unread 05-15-2015, 04:53 AM   #13
joe_jeep
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Im gonna give this a try! Cant wait to see pics, so I get a good idea how u did it.
Im ready to try anything to make mine more road friendly.
Its pretty much been parked since this Issue started.
I was afraid of ruining my new steering parts with the wobble.

sounds like a couple small heims, and a stick of small tube should do the trick?
is it a straight shot across under the balancer?

Soon, I hope to install a saginaw steering box.
I have a more saginaw box brace that runs to the opposite frame rail.
That could stiffen it some, Couldnt hurt I guess.
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Unread 05-15-2015, 11:16 AM   #14
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Wasn't there a semi similar part from nth degree that braced the frame at the trackbar mount? I can't recall how that one tied in on both sides. For the record I have the mm lifter blocks and no DW, not that it matters.
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Unread 05-15-2015, 12:25 PM   #15
MisfitSeven
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So if the frame can twist at track bar mount, can the steering box twist as well?

Also, where is the weakest point in the frame, where the twist is actually happening?
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