Well he said to go to the J/Y and get a driveshaft then do the Hack 'N' Tap. I was wondering why I couldn't just put the Hack 'N' Tap on the driveshaft I have on my XJ currently.

Sorry if there's something I'm missing. I don't really know much about anything vehicle related but I'm trying to learn!

 

Ok lets slow down... A sye is probably the best solution for solving driveline vibes, BUT... You have not done the lift yet.. I have a 96 XJ. I am curently at 3,5" lift due to DW issues and I lowered my rig as a road side repair for DW. I was at 5.5" and had no driveline vibes while running only 2" TC drop. At 5.5" I had zero driveline issues. The only reason I dont go back to 5.5" now is that I used the other 2" of my lift to lift my daughters ZJ.

Do the lift, do a TC drop, maybe shim the Rear. If you have vibes start planning the SYE.

 

If your drive line angles aren't too bad you could do what i did, and just get a longer drive shaft made. cost me about $170