Remorseless
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I definitely agree that caster is one of the first things you check, but it is not always the singular cause of DW. In general, my assertion is not that there is one singular cause of death wobble and it is toe - this is certainly not at all what I've asserted - but rather my assertion is that death wobble - which is an uncontrolled oscillation of the front axle components - can be caused by multiple components being either worn or incorrectly installed, and the behavior influenced by multiple other components, of which toe is one and of which caster is one. DW hasn't got a singular cause.
FWIW, you can roughly measure caster in your own garage as a layman without access to an alignment rack - Dana axle specifications specify that the vertical plane of the diff casing (most folks use the flats on the face of the differential housing, plug weld locations I believe, but machined flat), is ~6.0* off of the ball joint axis in the Cs - giving you 6* of caster built into the axle, physically. The realized caster will change due to the positioning of the axle and control arms at ride height, but is how the axle is assembled. So, using an angle finder on the flat on the face of the differential housing, you can calculate your caster - at least roughly.
Toe spec is between 0.05* and 0.35*, all positive, so technically only toe in. JLs are within spec from 1/8" to 1/16"-in by most recommendations. Mainly it's when running larger than OEM tires that aftermarket steering companies recommend 1/16"-out, with an absolute maximum of 1/8" toe out.
I would like to point out that I also never said just tighten things up - just to check that bushings are at torque spec. Ensuring things are at factory torque specifications - or aftermarket torque specifications, if an aftermarket component - is generally good advice that I will stand by. Not saying to crush it down, or to make adjustments to adjustable components - but just make sure the attachments to the frame and axle are at the appropriate torque spec for the part, per the manufacturer. And if it's a rubber bushing, make sure that the torquing was done at ride height with the weight of the vehicle on the suspension so that you're not binding the bushing. A rubber bushing on a control arm or trackbar that is entering and exiting bushing bind throughout suspension travel can cause death wobble.
I definitely also stand by the one system statement. Some components in the front end locate the axle laterally, some vertically, and some locate the wheels/tires relative to the axle throughout the steering arc, but it's all one system designed to keep the axle under the Jeep and allow you to steer and keep angles appropriate at the same time.
At the end of the day though, I think you're too hung up on caster. Caster is important - not arguing that, in fact if you look at my original post you'll find that I specifically called it out as a point to validate - but caster is not the be all end all of death wobble. My original post to point out that I did call out caster:
People need to know that rubber bushings must be torqued at ride height so that they don't do something like torque their axle end trackbar bushings while it's in the air and cause wild horizontal oscillations when they're constantly entering and exiting bushing bind driving down the street - causing, ya know, death wobble (and death wobble without impact to caster I might add, just binding and releasing of lateral axle movement, is a common issue with freshly installed suspensions). They need to know that exceeding the recommended toe-in spec can cause oscillations, yes that bad caster can cause oscillations, that wore out bushings can allow enough slop to allow oscillations, etc, etc. Focusing in on only caster doesn't check all of those other things that can cause death wobble.
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