I have a 1985 toyota Extra cab 4x4. I have had a vibration for a while and it has gotten worse. I changed out the two-piece driveshaft for a single balanced one and it improved some things but the same vibration is still there. It happens at different speeds, 35 - 80 mph. It seems to get worse the longer it is driven, up hills and in curves it gets worse. If I take it out of gear while the vibration is going on it changes nothing. I have swapped out the tires with my other vehicle, which has no vibration and no change. The cab vibrates like crazy the passenger seat shakes like mad, and I can see the back end of the bed shaking up and down on both sides. I have checked the bearing on the tail end shaft of the transfer case and it is fine. The only things I have not checked are the axels and axel bearings and the diff. and the clutch. Anybody out there with the same problems that found the answer? Any suggestions.