Metal slinky sound coming from exhaust when shifting gears up

[durtybubble]

(I have an aftermarket exhaust, this sound only started a few weeks ago)
It is almost impossible to get a video of this sound because it doesn't show up on camera, but its very easy to hear when I drive.
This sound ONLY happens when I accelerate (hard but not engine-ruining hard) and shift gears up. Does not happen when I start the car, doesn't happen when I rev the engine, doesn't happen driving normally.
At first I thought it was the exhaust rubbing against the rear diffuser so I sanded an exhaust shaped area down there but the noise didn't stop.
Checked all heat shields, none were loose, but just as an extra precaution I re-bolted some down.
It is coming from the rear of my car, not from directly under, which makes me believe it is NOT the catalyst.
I've checked all clamps, all seemed to be fine though I could retighten them sometime.
Exhaust is only a little loose under my car but only because of the hangers, not the clamps. The hangers are stock and I'm not sure what to do about those. Even though my exhaust is kinda "loose," when I shake it it does not rub against anything.


What could this POSSIBLY be.

 

[econoboxrocks]

You might need stiffer hangers.

 

[Handy Andy]

There may be a heat shield (corrugated metal) that is getting rubbed because the Motor mounts are now loosening up.

Does not mean rubbing directly - sounds like you're looking for that - it means the springs that hold the pipes are loosening too.

If you own an M/T - you'll know what I mean - some acceleration torque will shift the mounts and you'll feel the change in the shift pattern because of the change in torque.

So the pipes may make this springy creaking sound due to the shifting of lengths and twisting the pipes have to handle when you "beef" on the throttle.

That means a Gasket or two might have to be changed - nothing big, but you'll need to get with your helper so you can tear down the joints and look for the creasing or pinched or otherwise failed gaskets that if you used one that is similar to a metal sponge pad pushed into a round - that type of gasket crushes easily - might need to find another harder one to fix the creaking twist and hold its own shape better.