2005 Civic, MT, 120k

So last week my car developed a humming noise. I figured wheel bearing but the wheels are firm, no wiggle at all. Also the noise does not change when I load one side or the other when cornering. It's always consistant. Noise is not related to engine speed, it gets faster and slower depending on how fast I'm going.

So I put it on jack stands, took off the tires and started it up, humming noise is still there.

Here's what's kinda weird. I can hear the noise very well in the cabin. I cannot hear it outside. Now I have to give it some gas to get over 30mph for the sound to be loud enough to hear and to do that outside I have to be over the motor so that may be drowning it out, I'm not sure. When I have it idleing in 5th gear (about 20mph) and stand next to the tranny I don't hear any humming but the tranny doesn't sound smooth, I can hear the gears. Not sure if that's normal or not.

Clutch is about gone but I don't think that would cause a humming noise.

I had taken my car to Jiffy Lube to have the tranny fluid changed every 30k. This past time I decided to do it myself and used Honda MTF. Shortly after I did this the tranny started making a gear rattling noise when rpm's are under 2k. This was about 7k miles ago and hasn't gotten any worse. Now I have this humming noise on top....

Tranny is full. Shifts fine.