Sound general diagnosis needed, lifted 98 XJ

Got a 98 with 3.5RE super ride, installed mid July.
Had the HD SYE and CV put in as the stock rear output was toast and slingin oil everywhere.

I can't seem to get much motion out of the driveline when I try to move it around by hand.

Accelerating or decelerating I get a vibration that started out only being noticable at hwy speed right after had the lift put in.

Now after a couple moderate wheelin trips I get a noise that I think could be heard a few feet away as I drive by that sounds like a ujoint going. The vibration occilates heavier then lighter then heavier at about a 3-5 second interval cycling up and down. It is less noticable at hwy speed, but the occilation is more noticable, at low speed it is a constant vibration

The vibration *seems* to go away completly if I shift to 4H, and comes back as soon as I drop back to 2H (NP231 I believe, no full time notch)

Not detecting any leakage anywhere, I can turn driveline maybe a quarter inch worth of rotation on front and rear line but not getting any clanging, also seems to be very minimal side play.

Any thoughts?
Thanks much!

What are your angles (pinion, driveshaft and transfer case flange)?

Did you shim your rear axle? If so, what shim?

Acceleration and deceleration is shimming...

I'll uh, have to find out, kit was installed by a local shop

Would it be getting rapidly worse if it is shims?

it might be that one if not both of your shims broke or they might not be the right angle or may have slipped back some. or if it was installed by a less than excellent shop, there might not be any shims in there. check and make sure your driveshaft type and driveshaft angles match. they may not have the proper angle for the type of driveshaft you have in there. check these and get back to us 1. are there are any shims in there at all 2. are they broken 3. your driveshaft angles 4. your angles match the driveshaft type

Your probably binding up the driveshaft with the slip-yolk....mine did the same thing after putting a RE 4.5 lift on...only MUCH more severe than your talking about. Take your rear shaft off and inspect the slip-yolk looking for anywhere that the driveshaft might be coming in contact with it. The signs will probably be faint, so look hard...CAREFULLY grind away a little bit of metal off of the slip-yolk using a dremil or other similar rotary tool till there is no more binding. Its a bandaid, but it will get you by till you can afford an SYE. Shimming your pinion up will probably help a little bit too.