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Unread 04-19-2014, 08:19 AM   #31
skain8
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Look closely at the stock WJ steering geometry. Its not great. Not enough room for the engineers to fit everything (i.e. coils, trackbar, swaybar links, etc.) while achieving perfect geometry at the same time. Compromises were made, and lifting the WJ accentuates those compromises, which is why every damn thing on the front end needs to be tight and within spec or your steering will be even more negatively impacted.

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Unread 04-19-2014, 09:29 AM   #32
ezflip
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Quote:
Originally Posted by Darnice View Post

Steering arm is the adjustable arm that goes from the steering box pitman arm to the passanger side knuckle
The drag link, connects the right side knuckle to the left one.
The reason the steering arm goes all the way across the chassis to the other side, is to reduce the horizontal deflection angle whe then the suspension moves. Reduces lateral steering deflection.

I know its a lot of techinical stuff, but it all boils down to stopping the suspension, when it moves from moving in a plane that is not desirable. EG. If the suspension moves up and down, design to mitigate for and aft and lateral movement.

This is why the rear suspension does not DW, it has a fixed point of rotation in a horizontal plane. (the center ball joint) No mater how much you jack up the rear (to the limits of the ball joint) the axle will never move laterally.
Now, that being said, if you jack up the rear, and increase the suspensions angles from level, you then add for and aft axle movement, the bigger the lift, the greater the movement. Adjustable CA's can't stop that. The just fix pinion angles.
Umm, no. The bar that connects the pitman arm to the knuckle, is the drag link. Either way, the two bars you described are in no way, shape, or form parallel to each other.

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Unread 04-19-2014, 10:50 AM   #33
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Quote:
Originally Posted by Darnice
Its real simple, look at the suspension before you put on a lift. You will see the steering arm and drag link are parallel and move in the same arc plane going over bumps (thats why the pitman arm has a bend in it from the factory. Now put on your lift, and look at the same 2 links from above. Are they still parallel? No, do they move in the same arc? no. Why is this, well, you lowered the passanger side of the steering arm, increasing the angle across the chassis to the pitman arm. Sure you adjusted it to make it longer, but the angle stayed the same. No longer parallel with the drag link. That being said, what happenes now when the suspension compresses? The right front wheel will turn out because the steering arm is moving in a larger arc. The drag link, pulls the left wheel along with it. If the suspension extends, the opposite happens. pull the wheels the other way. So what is death wobble, its when you set the suspension in motion, and it begins to occilate back and forth between the 2 above conditions. A good track bar, well, again, if the suspension is lifted, its relationship to the above cross bars has changed and it actually causes the entire from axle to move left to right with suspension flex because its angle of arc has changed from stock. So if you notice the stock layout, all 3 bars move in the same vertical arc plane, when you lift the jeeps, that goes away, and DW can occur. So whats the fix, Well, a good alignment is a must and a good starting point. Adjustable control arms to get your pinion angles correct and axle caster are necessary, but even if they are perfect, it does not eliminate DW. So to stop DW, you have to get the links drag link, steering and trac bar parallal with each other. 1. Drag link, well its your starting point as it reference never changes no matter how high the lift. 2 . Steering arm, well must be parallel with the drag link, the closer the better, can be acomplished with a drop pitman arm, or a right side high steer kit. Either is fine as long as end up parallel to the drag link 3. Track bar, well drop the frame mount so the track bar is parallel with the other two at the axle end. Adding a longer bar to reach due to the lift actuall cause DW, because the axle is forced left and right every time the suspension moves. I talked about arc's, there are 3 in the front suspension geometry. Left wheel, right wheel, and both up and down. Change any one from stock, and DW can ensue. Everything from the factory move in designed arc's, as close as possible to horizontal. Why you ask, well if you look at an arc, the least movement horizontally is at the 90 degree part of the arc, then more you move away from 90, the more lateral motion is introduned for every bit of vertical motion. This is what DW is, the lateral motion of a suspension member moving in a vertical plane that is not at parallel position to all the other suspension geometry. On big lifts, 3-4 " you will be pushing the right wheel out with the steering arm on every bump, an pulling it back on evey hole, the track bar will be pulling and pushing the axle left and right on every bump. Soon the whole thing can start to occilate and DW happens. So the fix is not stiffer busings, or fancy track bars, or steering stabalizers, its to get all the flex of the suspension complonents as close as possible to horizontal and in parrallel with each other. Lets talk about suspension arms, if you lift your jeep, the arms, naturally, are now aiming down from the frame to the axle. they are no longer near level. Thus the travel has changed on there arch path, when you compress the suspension, the axle moves forward, and decompress, it moves backward. Ok, is this bad, well, yes, because the trac bar and steering arm are fixed to the frame on one end, So every time the suspension defects, the axle will be moved laterally, and the steering will move. Not good. Is it a design flaw, ABSOLUTLY NOT, but lifting has moved the geometry out of spec, and any vehicle will DW if this happens. This is why Chevy vans came out with drop spindles. Ever see a chevy van with lowered suspension that did not use drop spindles? DW on those can be very bad. So to combat DW, get your links as parallel as possible to the axle. and if your lift is very high, you may have to consider moving your mounting points for the control arm either lower or further away from the axle to reduce the arch degree change with suspension movement. High angle front control arms, whe the suspension compresses, actually cause the jeep to move backward, or the axle has to accelerate forward. This creates the Harsh ride when lifted, even with soft shocks and springs. All that lateral force is transmitted throught he control arms to the frame points and puts far more stress on the bushings than stock ride height does going over rough terain. This is why you see racing trucks, with very long control arms, massive suspension travels, but at racing speeds, the control arms are very close to horizontal. I know thats a lot of explination, but its to show ho one small change, like a simple lift can impact so may aspects of how the suspension and axles behave in the exact same road conditions. I should build a model out of lego, to demonstate all of the above, it really shows what your up against .
I love when people quote a long post in its entirety...
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Unread 04-19-2014, 11:51 AM   #34
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Quote:
Originally Posted by Darnice View Post
I know its a lot of techinical stuff, but it all boils down to stopping the suspension, when it moves from moving in a plane that is not desirable. EG. If the suspension moves up and down, design to mitigate for and aft and lateral movement.
Darnice... I can appreciate the thought that went into your previous post. I usually stay clear of DW threads, because I believe the cause is physical, so I believe there is no cure only the prevention that everyone thinks is a cure.

Caster plays a role in prevention so I want to touch on one part of what you mention.

The important part of the control arm fore and aft movement related to the 90* you mention is how it effects caster. The top arm is 14.9" long, the lower arm is 15 3/4" long. At both ends the mounts are staggered vertically. At the body end the mounts are about 7" apart, at the differential end they are roughly 8 1/2" apart. The UCAs angle slightly UP from 90 (horizontal with the frame), in stock configuration the LCA are 90 (horizontal) or slightly below 90. Because of that in the first few inches of lift you rapidly lose caster.

Once both upper and lower arms are below 90*, at one brief stage they work together so caster remains constant. Then because the UCA is shorter as you move further away from 90* the process will start to reverse. The shorter arc of the top arm will cause the caster angle to increase again.

As always I can be wrong but IMO...The at first rapid caster change because of the initial angle of the control arms is very likely one reason so many of the DW threads are with small lifts.

DW is a funny beast but a natural one, coil springs make it worse in violence because the whole car body can get in on the act somewhat like the frame and the rider gets involved in bike or motorcycle speed wobble. Speaking of that and having ridden countless miles on dirt bikes the below video cracked me up. Warning some may find this offensive but no redneck was harmed making this video.

https://www.youtube.com/watch?v=di3fpS5cem8
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Unread 04-19-2014, 01:11 PM   #35
sparky952
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Aye aye aye. I fixed my DW by tightening my trac bar bushing. I caused it by installing it loosely. My friend's WJ was resolved by replacing the worn and loose TREs. The FORD TRUCK AT WORK THAT ISNT A FREAKIN JEEP was resolved by replacing worn out bushings. All I an say is BIG RED FLAG captain obvious here stating it's not engineering it's worn parts. Straight axles that aren't properly maintained or screwed up by lifting will be out of engineered specification and therefore will act accordingly. Duh!
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Unread 04-19-2014, 01:16 PM   #36
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Quote:
Originally Posted by tinman77
yeah I totally agree. I just climbed underneath it tonight and sure enough it was loose again. Its strange how nice it rides after I tighten the nut down and how absolutely ****ty it rides when its loose. I emailed KOR tonight to see if they have any advice. What kind of socks are you running? I have the RC 2.2's, I took the rear off a few weeks ago because I had to replace the entire rear end. The shock felt completely gone. No resistance what so ever. I have a set of pro comps with about 10k on them that I bought when I only had a 2" BB on. Im wondering if they will fit with the 4" lift.
Are you referring to the trac bar jam nut? I had the same issue until I used blue LocTite thread lock. Just returned from Death Valley. Never loosened once I used loctite.

image-2771363059.jpg
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Unread 04-19-2014, 01:55 PM   #37
skain8
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Quote:
Originally Posted by sparky952 View Post
Aye aye aye. I fixed my DW by tightening my trac bar bushing. I caused it by installing it loosely. My friend's WJ was resolved by replacing the worn and loose TREs. The FORD TRUCK AT WORK THAT ISNT A FREAKIN JEEP was resolved by replacing worn out bushings. All I an say is BIG RED FLAG captain obvious here stating it's not engineering it's worn parts. Straight axles that aren't properly maintained or screwed up by lifting will be out of engineered specification and therefore will act accordingly. Duh!
Wow, you're a genius.
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'99 XJ: stolen
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Unread 04-29-2014, 11:01 PM   #38
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Quote:
Originally Posted by sparky952 View Post
Are you referring to the trac bar jam nut? I had the same issue until I used blue LocTite thread lock. Just returned from Death Valley. Never loosened once I used loctite.

Attachment 1276193
Yep, the jam nut on the track bar. This weekend I pulled the track bar and re built the bushings and made sure that I used the a mineral based lubricant and loctite on the jam nut. I also pulled the LCA's and adjusted to the recommend 16" center of hole to center of hole. Low and behold Death wobble completely gone!
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Unread 05-27-2014, 09:36 AM   #39
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So I had very little to no death wobble. Had new wheels and 265/70 tires put on this morning. Now it wobbles like mad. Went into full death wobble coming down a hill at 45-50 miles per hour. As soon as I fix one problem on this WJ another one arises. I want to beat my head against the wall.

So anyway, what are you guys finding to be the MOST common solution to death wobble on the WJ? I know there are lots of things that cause it..but on the Dodge trucks the most common thing is the steering box sector shaft bearing. Is there a most likely culprit on the WJ?

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Unread 05-27-2014, 02:54 PM   #40
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Do a dry steering test.
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Unread 05-27-2014, 03:11 PM   #41
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What's a "dry" steering test?
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Unread 05-27-2014, 03:26 PM   #42
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Quote:
Originally Posted by WXman View Post
What's a "dry" steering test?
Turn the steering wheel back and forth rapidly while someone else watches underneath for slop.

Turn the wheel from about 10:00 to about 2:00.

You want abrupt changes in steering input in order to really work the front end.

Do it with the tires on the ground.

Do it with the Jeep not running so there is no power steering assist.

If there is slop somewhere, it will be pretty obvious.
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Unread 05-27-2014, 03:33 PM   #43
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Ok yeah I am planning to do that as soon as I find a "helper". Oddly enough...out of all the Jeeps I've built this is my first experience with death wobble. I have heard that the WJ design is the worst with the wobble so I hope that this will be a quick fix and I won't be one of the guys that chases this forever. I'm tired of chasing problems on this thing. I just want to drive it!
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Unread 05-27-2014, 04:19 PM   #44
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If you have the cash just change all tie rod ends (4), track bar and any worn bushings on the control arms. I would also check wheel bearing assemblies and ball joints.

My issues where tie rod ends and I still have a little issue which I think is the track bar. With a 14yr old car pretty much every thing needs to be changed.
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Unread 05-31-2014, 05:46 PM   #45
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So I crawled under and watched while my dad cut the steering wheel back and forth. Couldn't see any movement in the track bar, TREs, or drag link ends. Control arms weren't moving either. Drag link does have a slight thud in it when steering. I moved my front tires to the rear and drove it and it will now go beyond 45 without death wobble. I still dont trust it but its better. So I am thinking tire balance, alignment, or steering box is the culprit on mine. Anybody have tips on what alignment specs to aim for?

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