300ZX 85 Turbo Automatic, Weird transmission noise?

[mellor21]

When I let off the throttle, my transmission makes a weird noise. Like a really fast papapapapa or tha tha tha tha, it's hard to describe. I believe that it's the transmission because it seems the sound is coming from directly below the center console. Could it be the catalytic converter?
This is the only car I've ever owned with an automatic transmission and I honestly don't know a lot about them. I've replaced the head gaskets, timing chain, and done a lot of other little things on this car so I'm not completely mechanically inept.
Any ideas? My transmission fluid looks fine.
It only does this while the car is moving, not if I rev it up in park or neutral.

Edit, does anyone know any faster moving forums for z31's? All of the ones that I can find barely have a couple of posts per day. Some don't have any activity for months..

[evildky]

How about the trans mount? Could simply be things moving around, have a good look at the mount.

[mellor21]

I'll take a look at it, thanks!