Originally Posted by 1slow370

if its a REALLY loud tin can could be bad clutch chatter and your pressure plate fingers could be bent or misshapen.

also the throw out bearing a little hydraulic cylinder with a bearing on the end of it that pushes the clutch in, when ever the dealer replaces a tranny the manual says they have to change it out so it probably isn't the real problem neither is the tranny unless you are getting two defective ones in a row(witch doesn't really happen). thats why i say i would suspect the clutch and flywheel if it is loud enough. some aftermarket clutches will chatter too just because they aren't dampened like stock ones are