[HGMOTORCAR]

Good Morning I recently received a 2001 boxster conv nothing fancy however I have encounter a strange noise a very light knock from the rear of the transmission housing yes it is a manual transmission. The noise is there at idle standing still with clutch pedal out when clutch pedal is depressed the noise goes away. I bought the vehicle due to an oil from rear of engine, cust declined repairs at the dealer and just wanted to sell the car as is. My question is I can't find anything on transmission rattles except when they come apart and by then its to late and since I have to remove the transmission to repair the oil leak I figured to do both at the same time, has anyone experienced this issue and know maybe what to look for.
Thanks in advance