I don't know what the sound is from.. I hope its not something big. Anyways... to get that sound, I would just accelarate normally and right when I feel the car is about to shift gears, I take my foot off the accelarator and a sec later I hear a "clunk". Is this just the gear shifting back down? or is this something bad? I get that often in city driving due to stop lights and cars infront of me... so... I just want to know what that could be.

Ive had this in almost all the auto's ive owned. Its where the box is half way through changing, then due to you changing the throttle position it decieds it dosent need to, hence the clunk happening.

You usually find that this only happens on simpler mechanical/vacum controlled boxes, and not on more modern electrically controlled ones, as these are far more precise and react a lot quicker....however the earlier style are much more reliable!

Hi Matt... will this cause any damage? Or do I have to wait till it shifts?

It shouldnt cause any damage, but, like me, you probably know when its going to happen, so all i can suggest is a light throttle or something like that, just so the bangs arent so harsh.