1995 chevy tahoe 5.7L tbi, 5 speed manual transmission.

I was leaving my road about two weeks ago, and right before grabbing second I got this loud grinding, and for the next half hour or so, at highway speeds I would get a short grinding/clunking when I went over bumps. This noise has come and gone over the last few weeks, and is completely inconsistent, in no specific gear, or speed. Accompaning this is a "ping" each and every time I begin to move, as if something is releasing (driveshaft/Ujoints?) and has since begun to do it with some shifts as well, as I let the clutch out or so it seems. All the while the other noise continues, but not as much as the first day. I have brought it to a tranny place and they said it's not that because it's way to inconsistent. If anyone has any thoughts, please feel free to lay it on me, I'm just looking for somewhere to start looking.

Thanks a bunch.