A500 vibrations

Time flies when one's having fun but who wanna have a boring time..? So anyway, I only have almost 8 miles to work & I only go there 4 days a week so ofcourse I drive as I can take it easy & notice any changes...
& by now I'm sure the vibrations have to do with speed; when I take it easy it comes when it gets close for 3:rd gear to kick in & if I drive more like "todays stressy trafic" it starts when it goes into 3:rd gear.
So now I'm in doubt if it really is the bearing closest to the driveshaft... Any ideas?