HELP - vibration in the driveline

Sounds like you may need new U joints. Slide under the car far enough to grab the driveshaft and see how far you can turn it. If you can turn it 1/4" or more and you can feel a clunk when it stops, it's bad U joints. I usually don't even bother trying to figure out which one is bad, I just change them both. It's cheap insurance. A U joint failure will either beat the crap out of the bottom of the car (rear joint) or cause the car to pole vault (front joint).