Transmission noise (sound like bearing failure)

ronstoppable

I had my car now for 2 years. I drive about 100 miles round trip a day to and from work. The car now has 44000 miles on it. Mainly all highway. Approximately 20000 miles ago I experienced a noise coming from the underside of the car when i release the clutch and the car is in neutral. I could really hear the noise when going through a drive through as the noise bounces off the wall. I took it to a dealer and they told me the input drive bearing sounds bad. Being under warranty the dealer put in a new transmission instead of rebuilding the old one (cheaper for Nissan). Now I'm experiencing the noise again and it seems as if its getting louder. When i take off in 1st gear very slow it sounds really bad as if a bearing is grinding. All in all though the car drives and shifts fine and the clutch doesn't slip. Also, when i depress the clutch the noise goes away. The car is still under warranty so i am going back to the dealer about this, but before i do i would like to get other peoples input. Thanks :-)