The angles have to cancel each other out. You could have a ujoint operating at an angle one degree shy of where the yokes bind, and you could have absolutely zero vibration at that extreme angle IF: the ujoint at the other end is at the same angle AND: the driveshaft is long enough for good slip yoke engagement. With a 2 ujoint shaft, the angles have to be equal or maybe one degree down from equal on the pinion end to account for pinion rise under torque.
With an SYE = 3 ujoint driveshaft, all the angle compensation is taking place at the transfercase end of the driveshaft. The angle is split evenly between the two joints in the double cardan assembly while the pinion should be pointed straight up the shaft- or one degree low for pinion rise, same as a conventional driveshaft. Interestingly this causes SYE users with proper angles to have accelerated rear ujoint wear. Why? Because the needle bearings don't really move around as there is near zero angle. This can cause a brinnelled spot in the ujoint and requires more frequent greasing.
So, given a 97 with a 3 inch lift and stock shackles the pinion angle will probably need to go DOWN 1 or 2 degrees to achieve the perfect parallel angles. However this isn't gonna work because the slip yoke is now pulled too far off the poorly supported end of the rear output shaft. The limited spline engagement causes the upper end of the driveshaft to track in an ellipse, setting up a vibration- angles be damned. Then you get the nasty transient noise on trailing throttle, when there is neither accel or decel torque being applied through the poorly engaged slip yoke.
The answer? There are two, either tcase drop or SYE. I frankly don't like hack and tap SYE's, the HD SYE is the only way to go. There have now been so many of them built that the tooling was paid for long ago and we're paying less for them than 10 years ago. The junkyard front driveshaft option is a good one. XJ front shafts are .120" wall and well balanced, which you can't always say about the aftermarket ones. The factory front slip spline is weak compared to a custom shaft, though, but if it makes it more palatable to use a $20 dollar part to get you by until you're ready for the $300 one- perfect. Then use your old one for a spare for front or rear once the custom shaft is in hand.
. I just lived with my vibes, but SYE isn't to far away.
