front right hum increasing with speed - not wheel bearing

I'm new to the forum, I have a 2004 Prius with 225 000 Km and it runs fine, no special noises. I just bought a newer 2009 with 321 000 km, it runs fine, but I discovered a humming noise that increased with speed comming from the right of the car. I suspected the wheel bearing, but when I removed it, it seemed very fine. Changed it any way, but still have the same sound. When at a speed of 90 Km/h on the highway if I turn slightly left sound is a bit louder, slightly right sound is not as loud. Checked level of tranny oil looks ok. I was thinking maybe my right side transaxle (i noticed a small grease leak from the boot on the transmission side of it), what do you think of simply swapping one another and seeing what happens. I was told the process is fairly easy, simply having to remove the shaft from the bearing, and then pulling it out. Is it true that I can just pop my 2004 one out, then pop out the 2009 one, and then pop in the 2004 in the 2009 or is it way more complicated? Many thanks if some one who has done this before can explain, Louis

 

I'm sorry just noticed that this ended up in the bad section, can anyone assist me in moving the post to the gen2 Prius section?