05 Mercury Grand Marques. Had a rear wheel bearing replaced. Within a couple weeks, it was humming again. Took it back to the guy and he put another one in. After 20 miles, it's humming again. Anyone have any experience with this sort of issue? He's done many of these in the past and has never had this issue.

 

There could be an issue with the axle shaft since that serves as the race for the bearing.You could also try another brand for the bearing since there is a lot of Chinese junk out there.