The chatter is loud and usually much more noticeable when the AC is running. According to UUC you can cut down on this chatter with a mix of redline ATF/MTF. I did it for a while before I changed to straight redline MTF. It may have been a little quieter with the mix but not really sure to be honest.
You can pull back on the gear shift lever a little too and it will quiet it down a bit. if it were related to the throw-out bearing it would be more of a grinding noise than a chatter and it wouldn't matter if it was in neutral or not.
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