I had the original transmission fail on me and was pretty quiet. I found a used one on the junkyard and mechanic installed it, now its making this noise what could it be? I had the mount replaced on the old transmission 50k miles ago

The faster I go the more noise it makes

Video: https://www.youtube.com/shorts/l71dVklv8uk

 

No clue. Get it up in the air and see if anything stands out. If you make another video, put it manual mode and show the tach, speed, and gear. That would be helpful.

It sounds to slow for engine or driveline, almost as if its valve train which is 1/2 engine speed. Open the hood and listen. Maybe shove phone under hood and drive?