944s2 transaxle rattle

When the car is idling in neutral and the clutch is engaged, there is no noise coming from the transaxle, but when I let the clutch out in neutral,  I hear a rotational noise coming from the transaxle. New clutch 3 years ago. I changed the transaxle gear oil with sae 75w-90 full synthetic 3 weeks ago, but same noise. The gear box shifts are smooth as can be. I heard using Swepco transmission oil might quiet it down, your thoughts.