a couple days ago, i started experiencing a strong vibration when im driving. i thought, that maybe the driveshaft was hitting something, but everything seems clear. i can only feel it/hear it when its in gear and above 20 mph. i keep checking to see if im rubbing, but everything looks normal. also, it only happens when my truck is in gear. when im going down the road with the clutch pressed/out of gear, it rides as it normally does.

any suggestions on what it could be?

my rig is a 93 4runner, 5spd.

 

u joint