6" Lift 2007 Tahoe Issue

Just got done lifting my 07 Tahoe with BDS 6" and 2" body kit and am experiencing a vibration only from 15-30 mph. It vibrates when accelerating and when coasting to a stop. Have tried adjusting driveline angle with adjustable upper control arms in the rear and have also replaced u-joints to no avail. Any hints or help would be greatly appreciated.

Has anyone ever had problems with driveline angle from transfer case to rear axle??

Does the whole car shake or does it feel/sound like something specific is shaking?

What do you mean by driveline?
The shaft? I don't think adjusting the control arms would have any effect on the drive shaft

I lifted mine 6 inchs and the angle from the transfer case on the rear differential is not too bad/ scarey looking

Take a picture of yours and I'll post a picture of mine, the drive shaft angle that is

What's vibrating? Entire truck,front end,corner,steering?
Could be a number of things. Out of balance tires/rims,bad belt in tire,out of balance driveshaft,ring and pinion backlash loose,alignment,steering parts (knuckle,wheel hub,tie rod ends,etc). If you put a 6" suspension lift on,it should have come with a drop down bracket kit for the transfer case to reduce any bad drive line angles. I have 6" Rough Country lift on my 2000 Tahoe and had no bad drive line angles at all. The body lift alone could be vibrating. Body lifts are so bad for vehicles. they just where cab bushings out prematurely. Most likely you have an alignment issue. Whenever you lift or lower anything,all specs go out the window.
What size tires you running? Find a good alignment shop and have them check your caster alignment. 2 degrees positive is factory spec normal. More details would be helpful.

So I adjusted pinion angle and vibration has decreased greatly. I measured angle of rear diff and it's at 9 degrees. My upper control arms are shortened as much as possible but diff needs to come down a few more degrees. Does anyone know what they should be set at? My tc case angle is at 4 degrees.

I also rebalanced all the tires to rule that out and alignment was done. Running stock rims and tires until I can fix this vibration. 265/70/17. Looks ridiculous but don't wanna throw my 35x12.50x18 on until issue resolved.

The only vibration is coming from the rear from 20-27 mph. I talked to a shop that said if changing angle doesn't help they can replace u-joints with cv joints for a nominal fee.