low hum in driver train starting at 45 mph

When I bought the truck, I had read that it could be a little noisy at speeds above 60 mph but about a month ago I started to hear and feel it starting at 45 mph and more audible than the original noise. I am 2 1/2 hrs. from the nearest dealer and have procrastinated doing something about it. . I received an e mail from Tacoma World that there may be a bulletin on the issue. I have not received anything from Toyota as yet. My truck is a 2012 , 4 wheel drive , 6 cylinder that I purchased in October of that year. How common is this problem and what can I expect to be done.