bad vibrations

You sure its not coming from the transmission if not have the tires/wheel alignment/suspension checked out-

Suspension-related vibrations will be much lower in frequency. High frequency vibrations are caused by the drive line, typically tight universal joints. Look for signs of reddish-colored rust around the bearing cups. Whether you see them or not, you'll have to unbolt the rear joint and remove it to check for tightness and binding in both of them.