Well, I think it's time to just get a new transmission; saw some black colored fluid puddles on the ground beneath it; I'm pretty sure it's mostly from the transmission fluid that leaked out mixing with the grim on the transmission's belly. The reservoir was almost empty so I topped it up and drove around, but the sound is still there, unsurprisingly. Here's a video so you guys can hear it, maybe someone will find it interesting.
https://www.youtube.com/watch?v=O49s0ooywbI