my bandit

iTrader: (10)

i know i have a slight knock (any way to fix that?) but what is the griding type sound? it only happens when the car is cold and either in drive with the brakes on of idle speed with no acceleration. it sould somewhat like metal on metal griding and it just started, i replaced the transmission fluid and filter about a year ago and it doesnt smell burnt. the sound goes away after driving and it doesnt get louder at acceleration
http://www.youtube.com/watch?v=ETCkR8yz7Dk