You know, I have the same thing except I haven't changed or touched the wheels or brakes. It makes this noise occasionally, not all the time, but when applying brakes or slowing down to a stop...then I hear the thump, or it sounds like something disengaging but not the transmission.
I also sometimes get a binding clicking sound when first applying brakes when the VX hasn't been in use for a while. Everything works fine though so I have no clue what it is or whether to care about it??
Anyone else get this?