1997 GT rear end noise. VIDEO to show noise. Need Help

Hey guys, I have a 1997 Mustang GT with 145,000 miles on it. I had mentioned this is an earlier post with other things, but now I have a video.

When accelerating quickly, I hear this loud "creaking noise" that is super annoying and definitely isn't healthy to say the least. This is the best way I can describe it, or maybe something rubbing?

It also happens when I take a hard left hand turn, so I know it's coming from the right side of the rear end, it doesn't happen when turning right. As a result of hearing it in this situation, I don't think it has to do with the drivetrain, although the video might make it sound like that. When spinning the tires, I don't hear it cause the rear isn't under very much of a load.

As far as I can tell, plus 2 other mechanics mechanics that I went to, the shocks are good. When suppressed, they bounce up once and both sides come up evenly with zero noises. But that was all we tested.

What the heck could this be? Which bushings? Or could is still be the shocks? Torsion bar?

Any/all help would be great; I just want to replace whatever it is ASAP.

Here is a video of the car with the back seats down under hard accelerations 2nd gear, I hope this helps.

Noise coming from rear end 1997 Mustang GT - YouTube

Thanks!