06 Jetta TDI Tranny noise in Park

When I park my car even on the slightest of inclines (of course I apply the parking brake) the car sometimes makes a funny noise when I put it in park. Not to mention it trys to roll forward a little bit. It acts as though the transmission is still trying to engage, or under a load. I then have to apply a little bit of force to put it in N to make it stop making that noise and retry to place it in park. At this point it usually stops making the sound. The sound it makes is a loud humm.