heavy vibration

99 4.0 MT 3"on30s
well couple days ago it started with a chatter of metal. now there is no chatter but a lot of vibs. it gets the vibs from 25mph on. and is a consistent during accelerate and down shifting. when the clutch is in or its in neutral it feels like the vibs are go away.

ujoints look good rear was just rebuilt trans mount seems solid. i don't see any cracked spring mounts but im going to take a better look at them tonight im not sure where to look next.

any ideas?

most likey a driveshaft bad u-joint. did you check the u-joints for play/movement or just a visual check?

i pushed and pulled but im going to remove it and drive around see if there is a difference.

Sometimes u-joints seize up and have no noticeable play, but are unable to turn, causing vibes/shakes. Only way to tell is to remove the shaft and bend it by hand.