When I start driving, every gear sounds smooth and healthy going into except 5th gear! As soon as I enter 5th it almost sounds like a bearing that spins? Also as I excelerate upwards to 70mph the sound goes away. I run premium octane of course. I do not think that it is the throwout bearing, but I also do not know a whole lot about clutches/trannys. The car has 44k miles, and has 3:73 gears. Please help...