S 60 humming noise on left side of car only above 20 mph

[Al]

I have a 2002, S60 non-turbo, When I get to about 20mph a sound similar to bad wheel bearing or bad tired humming sound starts. The sound does not change with speed and or direction of the of the car which probably eliminates the bad bearing diagnosis. At cruising speed if I place the shifter lever in neutral and let the car coast it continues making the noise. I have rotated the tires to eliminate the "bad tire" guess.

I understand the transmission is on the left side of the engine compartment and that may be the culprit. Is there a bearing that maybe causing the noise??

Does anyone have any test ideas. I recently purchased this car in Seattle but the car came from New Jersey.

If I lean to the right when driving at cruising speed the noise almost disapears which means it must be isolated to the left side of the drive-train.

Anyone have experience with this?

Thanks for your assistance and ideas!!!