We're pretty sure we've got a wheel bearing going bad in our 2003 Corolla, but we can't pin down which wheel bearing it is.

Help? Could it be something other than a wheel bearing? Are there any other tests I could run? Should I just start replacing them one by one?

It groans at higher speeds, and the groaning noise (and the vibrating noise) pretty much dispppears when veering to the left.

I don't really know what I'm doing, but no wheels seems to have any play from what I can tell. We dissassembled both front wheels to the point of sliding the axel out and spinning the bearing, neither seemed to make any weird noise or feel particularly grindy.

The driver side rear wheel seems to make the oddest noise when manually spinning the tire, but I can't tell if it is just the brake rubbing a bit.