The best way to get your proper caster angles is on an alignment rack but you can get very close if you know where to measure.

The stock JK front housing is designed for 4* of caster and 2* of up pinion tilt for a total 6* of separation. Measuring your pinion angle will give you your caster angle. If your pinion is measuring 0* you have 6* of caster.

 

I'd imagine that the rest of the vibration is from your tires. How about totating the front to the back and seeing if it changes. I had a vibration with mine that was stubborn, turned out to be one of the tires. It came up on the balancer as dead on but when I finally pulled it and moved it to the back the vibration was gone. My vibration was right at about 60mph.

 

The ideal caster to minimize driveline vibration on the stock shaft is straight inline correct? I plan to use the adjustable uppers coming from Northridge to dial back the caster until the vibes disappear... hopefully!

I don't think much of the vibration should be coming from the tires, I've been running balancing beads like these from 30,000 miles or so with good results. No weights on the wheels at all right now. I guess I'll take it one step at a time.

Thanks,

RT