Driveshaft(?) Troubles

Hey all. Ive done some work since my intro, finish the body work, rattle can od green, black front end, and put a pioneer system in it. Recently there has been a grinding/squeaking noise coming from under the cab and some vibrating at lower rpm. I was thinking it could be the center bearing? But I read somewhere that it could be the tranny. Im gonna take a look under it tomorrow.

Below is my truck and my other project. 1989 suburban with a bad tranny

Take a close look at the U-joints. If they are original, they are probably tired!