Vibrations...Help!

Hi guys, its great to read all ithe information yo uguys post, all i can say is wow! i have a vibration problem...always had it in this used truck i bought, forst thought it was rearend, changed the tires no change then a friend asid read, changed carrier abd penion bearings, no change..mean time new clutch kit and support bearing, no change ..all the ujoing feel tight and i just cant figure what else it is, ujoints or bent driveline but when its running in geat on the rack all looks and runs smooth no visible bend or out of roundness. anyone have this problem ., any ideas ????:headbang: