2007 Z4 3.0 Si equiped with a 6 speed manual transmission. When cold, in nuetral and clutch pedal engaged or disengaged, no noise. When warmed up, in nuetral, no noise when clutch pedal pushed in (disengaged) but when the clutch pedal is let out (engaged) there is a distinct rattling/chattering noise. No noticible vibration. The car is still under warranty (43K). Dealership unresponsive to check if the noise is symptomatic of input shaft bearing issue, throw out bearing or clutch problem. Don't like the rattling/chattering noise and am concerned about a transmission problem developoing after the warranty expires. Diagnosis and/or suggestions?