thought i had a bad front u joint because of clinking and vibration. the rear one didnt seem to be the source so i pulled out the driveline to look at the front one. It seems fine in my hands can you visually tell if a u joint is bad?? could it be the rear end?

 

the yoke has rust going back on it about an inch. is that a problem? it has a sticker on it from a local driveline shop i'm wondering if it was made to specs. is there a difference in length of driveshafts from a manual or automatic? (85 gsl)