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 .