whats up guys...over winter i picked up anluminum driveshaft. put it on this weekend and did some test runs and now when i drive it going up the gears or downshifting and in netural it feels like stomehing is slapping my seat...i can feels the vibration through out the car. sometimes it suttle and sometimes it bad...i jack the car up and noticed it spinning unevenly...i just can put my finger on it??? any ideas...joints are tight as heck....all of the clips are on both ends...