I have a 90 Miata 137k.
The rear end groans as I take off or get crossed up. Sounds like its shifting subframe to body but I have double checked the bolts. No sign of movement there.
Is it just normal? I tightened my roll bar bolts, My shock mounts.
The a arms have poly but I don't think its that. I have a noise I get when the drivers side suspension moves up and down that is the poly bushings. That I am not worried about.

Its not something that happens every time but the first pull out of garage when I get crossed up on the alley. The alley is sloped into the middle so water flows there its a little steeper slope than your regular alley but nothing crazy.

I have changed diff bushings in the last month. Went with mazda comps there.
It made no change to the noise.

I don't know what kind of help yall can give me. Hard to diagnose some noise thru "the series of tubes" that is the internet.

 

I don't know if this will help, but I had a creaking at take off that was fixed by switching to delrin door bushings. I really didn't think door bushings would create a noticeable change, but they did.

 

Do you have a hardtop? Take your sway bar off and see if it still makes noise. Squirt some penetrating oil on stuff. You know, trouble shoot and figure it out.

 

Many peoples rear's make odd noises when they move about. And penetrating oil, while popular, does not alleviate this. Try a bit more fiber, some good fresh garlic, and less yeasty foods.

 

Well played.

 

Take it from a pro; don't use any warming lube in the rear.​
The sensation is... interesting at first, but you need things to be cool in the long run.
Check your u-joints. They last for a very long time in a miata, but they occasionally go bad.
I recently had some go bad, and I would hear a metallic clank when going into first.