I got a strange noise question?

I hope someone can help or offer some advice. I tried to search for the same problem but didn't find anything. I have only had my car 2 weeks and I knew it had a bad tranny mount. Tonight a friend of mine and I changed the mount. Afterwards when I went to leave I started to notice a strange noise either a type of vibration(maybe a heat shield) or scraping coming from the passanger side. The weird part about it is it only does it when I am slowing down. If I am on the gas no noise just nice and smooth. I thought it was the brakes at first because I first noticed it when braking to slow down but then realized it happen when just coasting. This just started after changing the tranny mount. If anyone has had this problem or any ideas I would love to figure this out quickly.

Thank, Joe