lshmmm

I've got a rattle that I can't find info on. Please read everything as I do not believe this is a common rattle.

I've done the following diagnostics:

• recreated the condition on a lift and listened from underneath using ears and also a stethoscope-screwdriver.
• applied tension and traction to middle-exhaust hanger springs.
• Applied JB-weld type stuff to loose 02 sensor hat to secure it.
• Shaking the exhaust by hand
• shaking the exhaust with a hammer and a rubber mallet.

What:
It sounds like either very small pebbles being through around in a vibrating metal container with thin walls. The frequency of the rattle is proportionate to engine speed. It is quite loud and persists until the engine reaches idle.

When:
It happens only off throttle, as the engine speed winds down and then terminating at idle. It happens when the car is stationary or moving. It happens when the clutch is engaged or disengaged. It is not noticeable only when the engine is cold. I can only hear it at engine speeds below 3,000, but it may simply not be audible over the sound of the engine and exhaust. I cannot recreate the rattle by moving or hitting the exhaust.

Where:
It sounds like it's coming from above the middle exhaust hangers where the torque tube marries the transmission.


I've ruled out:

• H-pipe jingle
• middle exhaust hangers
• transmission
• catalytic converters.

Suspicion of the 02 sensor hats is low, because the noise does not sound like it's coming from that area. I haven't ruled out the hats on the 02 sensors. I shoved a bunch of JB weld-type stuff in there, but I didn't' remove the mid pipe to do it and I may not have done a great job. The problem persists, possibly ruling out the 02 sensor hats.


So... what else could this possibly be?

lshmmm

Bump. Anyone?