I have that same drill and the top cover does make a racket. Pop the top cover off and run it. If the racket is still there then remove the belt and run the motor while using a stick to flex the lower part of the cover, if the noise is still present and you can't nudge the cover away to make it quiet them you got problems on the motor end bearings or balance. If quiet with the belt off and the motor running then turn off the motor and turn the spindle pulley by hand to feel if the bearings are bad or the pulley is hitting the cover tin. One or both of the pulleys could be to far down the shaft hitting the cover, or a dent in the tin, or pulleys to big.
lg
no neat sig line