[Blacdout96]

1. Check and see if you lost a weight on the driveshaft, or any obstruction stickign to it, that could make it vibrate.
2. Just like head lights, replace U-Joints in pairs to assure that the other one hasent taken a dump.
3. when was the last time you looked at your differential, or changed the fluid, maybe a bearing or gear tooth/teeth maybe damaged?

As for your trans, maybe a good bleeding or maybe a bad slave cylinder that's stuck?
Also, how does the trans mount look. Don't just visually inspect it, take it out and look at it. Hows the trans fluid, is there shiny specks in it?