Horrible, loud, clunking noise coming from rear - 350z
 

Video: https://drive.google.com/open?id=1EU...ZPzypp3x5em9fj

Does anybody have any idea what this horrible clunking noise could be? Kind of developed over time and now its gotten really bad. I've had it now for probably a year and its gotten worse.
I could not find anything like this anywhere on the internet for some reason.

Note: its not the trunk trim pieces, axle shafts, exhaust and likely not the sway bar end links.
Only thing modified with my suspension are OEM style coilovers.
Other than that I have no idea what it could be

Differential bushings

Don't mean to sound rude at all, but do you know this for certain? The rear diff bushing is definitely worn on my car.

Try driving with the hatch up, see if the sound goes away. My car makes a similar annoying noise and it's from where the hatch shock mounts to the body. I made my own gasket out of rubber hose to fix this issue, and it worked for a while, but the noise came back.

If it's not that, try and tighten the rear shocks from the upper mounting point, in the rear wheel well.

The noise does not sound like a clunk from the diff, or sway bar end-links to me.

When the aftermarket suspension was installed, did you replace the gaskets at the top of the rear struts? Or are you running your coilovers with metal on metal? The OEM gaskets are notorious for drying up and falling apart. I replaced mine with Neoprene (1-2mm thick sheet) I picked up on Amazon and cut to fit the strut hat, worked great.
-Icer

The sound is still there when trunk is open, but less. Leads me to believe its not coming from there, but whatever it is is still affecting the hatch too. I tightened the upper shocks too, so still not really sure.

I agree with Painterguy39. It sounds like a failing differential bushing. If this is the cause, you would also experience a loss of acceleration (but, possibly not obvious since it occurs over a long period of time - possibly years)

Man I really hope so. I ordered the Z1 Motorsports polyurethane bushings and gonna replace them over the weekend. I’ll update when I do it.

Bro did the bushings help?

It was my clapped out coilovers, i took off the rear struts and the noise disappeared!