I haven't yet. I just bought this vehicle not to long ago and am trying to fix all the little bugs.

 

I have the same problem. 87 blazer 4" lift. vibration after lift kit install. Replaced both u joints on drive shaft. still have the same problem. the drive shaft looks ok. Need to get it balanced?

 

Your problem is probably due to the increased angles in the driveline. Did the lift kit include a correction in pinion angle?