What is this #$%^*&@ noise?!

[elkaboom]

First off, a little background: the car is my daily driver -a 90 LS AWD 4eat with 200k (just turned 200k btw).
In any event, a very peculiar, rather unsettling noise has recently began emanating from somewhere suspiciously near the TC. At first I thought it might be a loose cat or something vibrating aginst a cross member or possibly, something shaking loose and banging against the undercarriage.
Last weekend, however, I put the car up on ramps, and tried to localize where the noise was coming from. I've definitely been able to determine that it's coming from somewhere directly above the tranny fluid pan.
THe noise in question is a loud, intermittently repetitive banging, clanging... think, "tang, tah-tang, tang, tang, tuh-tang, ting, ting, ting, tang, tuh-tang" ad nauseum. It's generally constant once it starts, but occasionally, I'll start the car and it'll idle normally without any noise but as soon as I shift the car into D or reverse, the nosie will start up and then it's pretty much constant. Also, the noise is generally only present at low idle or in park; at highway speeds you can't hear it (that may be due to road nosie), but even when I put it in park, if I step up the idle to 1000-1100 rpm's, the noise will disappear. Of course, once the car drops back into low idle, the noise stars back up again. It's fairly loud, as well. Other than that, the car shifts normally, doesn't cut out under acceleration, isn't leaking fluid, burning it, or doing anything else out of the "norm". I have had intermittent torque bind issues with this car for years, and I have what I assume must be some kind of valve body buzzing (duty solenoid possibly?) during acceleration -also present forever.
I'm totally vexed and sadly, waiting for the tranny to take a big crap, because it sounds like something has broken loose inside the tranny and is banging around inside the tranny pan or within the torque converter itself. This is my daily driver, again, so I'm nervous. Any ideas, suggestions, or advice?
Any and all input would be welcomed at this point.

[jefferson]

I would check the bolts holding the flexplate to the torque converter.

Jeff

[gijonas]

I would check the bolts holding the flexplate to the torque converter.

I was just about to type this.Other than that probably internal.

[ericem]

Today it was so weird I heard clanging, clicking sounds, almost sounded like the motor. I popped the hood and found the flexplate bolt access cover had fallen inside and was bouncing around and hitting hte flexplate. Got some long pliers and yanked it out.

[elkaboom]

Funny you should mention that, because my access cover for the TC has been missing for years -I think it just fell off one day, and I never bothered to replace it. In any event, I'm beginning to wonder if something didn't fall in there; perhaps a small rock or something along those lines -it would certainly explain the banging which, incidentally has all but stopped for the moment. It'll still make the noise occasionally, but it's nowhere near as loud or as pronounced, which leads me to believe that something may have, in fact, fallen into the access hole.