Violent Vibration and sometimes clicking 2000 Blazer 4x4
 

Wats up guys I am posting in here as a last resort..Ok I have a 00 blazer ive been chasing problems on since I have acquired the truck..most recent problem was a whine/tea kettle sound which I thought was the front end but from numerous checks etc realized it was coming from back or in the middle of truck. I checked back brakes have been replaced both front and rear ebrake adjusted. Noise still there, so I decided id replce the drive shaft from a parts truck..Noise Gone...Good deal ok but a couple days later im driving and the truck just starts vibrating violently and making a click/chirp sound which is typical for a Ujoint ..Cool threw other shaft back in no whine go around the block and mash it ,nothing. Next day I take wife to work about 4 blocks and its back same vibration and clicking sound..So much question is could it be my ujoints on both shafts? or is it something else..no play in rear diff at pinion at all..front wheel bearings have been replaced along with all front end ball joints,idler,pitman even new gear box tie rod ends etc..

I drove today and it would not do it..im at a loss have no idea what it could be ..also no play in cv axles at all good tires always at correct psi..

Do you guys have any idea what this problem is? please help..thank you

also all fluids are good have been changed and no leaks im stumped..no uneven tire wear etc..thought was 4x4 partially engaging but ive verified it works fine 2hi,4hi and 4lo ..all vacuum lines are in correct place ..please help guys thank you