i had a very annoying "squeak" at 0- 10 mph and a vibration over 55 and could not figure it out. i turned the yoke 180 with no results. i finally decided to put the driveshaft from my parts car on. when i took the driveshaft out one of the caps fell off to reveal burnt needle bearings. i put the other driveshaft on and no squeaking and no vibration up to 75.

just wanted to post this in case anyone else has the same problem.