Go Adams. If its flighty then they didn't adjust caster properly.

 

They re-adjusted the caster (eye-balled it) to test if the front DS vibration would go away but they were very transparent that I couldn't have both, a good caster angle and no vibration unless I got aftermarket DS. Never heard of Adams, now getting more confused by all the different brands and types.

 

Ok did they say that because your driveshaft is bad or did they just say that as a fact or what they believe to be fact? Cause if they just stated as a fact then take it to another shop cause they are wrong. Actually I say switch since they are eyeballing stuff in the first place l.

Adams, coast, j.e. reel, Tom woods = all good.

 

That's not 100% correct. The stock shaft should not vibrate unless damaged. A aftermarket DS requires a balance between caster/pinion.
The easiest way to determine front shaft issues is to remove it.

 

Driveshaft is not damaged. As context, I had a low end 3.5 Rubicon Express kit with cam bolts. Replace all but springs with Synergy (basically short arm kit). To complete kit installed Synergy 4front/3rear springs (mainly to remove rake) and now I get a driveline vibration between 68-80mph. My caster has been set at 5-6* for over a year (most recent at 6.2*). The shop thought the vibration was caused by the extreme angle so they turned it down to about 4* or so but no change to vibration. Shop removed front shaft and no more vibration. There is no evidence of the DS being damaged accept the flange seal is freshly torn and getting some grease splatter.

I know there is no guarantee a new DS will fix it but I've gone to 3 "local" shops who are supposed to be top experts with lifted JKs so I'm beyond the point of frustration.

 

With that much lift it might be a good idea to get an aftermarket anyways just for the simple reason you already stated, a torn boot. That's a common issue at the height and why I decided to stay below 3" of lift.

 

Seems to be consensus that with aftermarket DS caster angle over 4* can vibrate. I'm trying to maintain 5-6* so that's not preferred for me. Anyone running higher than 4? Maybe I should change drop the height .

 

I know people that have drive shafts from Coast, they're quality is fine. Chances are the other ones are fine too. The thing I liked about Tom Woods was their much shorter flanges, which means the drive shaft is a bit longer, which in turn means the u-joint angle is smaller. Both flanges together end up allowing for a drive shaft that is 2-3" longer than most others.

 

I have a similar set up:

3" synergy springs with 1" soacers up front (actual measured 4" lift all around)
Synergy lca
6* Castor
5.13 gears (so very fast spinning driveline)
Tatton 1310 front driveshaft

No Detectable Vibrations up to 90mph. This shocked me I expected to have to lower my castor but it works for me don't know why it seems like it shouldn't, lol