My truck did the same thing with the exception of the pulling, I could hear the hubs when I was driving the sound is almost like a whine that matches your acceleration. My vaccum hoses were bad and by the time I diagnosed the problem both hubs had to be replaced (due to being engaged when driving) along with the bad vaccum hoses. I didn't have time to fix it so I took it to the dealership and they told me water can get in hoses and create the problem. If that is whats wrong with your truck I would fix it asap.
Check the solenoid. Yesterday my truck started making this buzzing/grind noise while going down the road. I took it to my mechanic and he replaced the solenoid. It could be what you are experiencing. They get water in them, I guess and it ruins them. There's a TSB on it I guess.
2005 Ford F-150 Lariat Supercrew (dark stone metallic) - Corsa DB Exhaust
1994 Chevrolet Camaro Z28 (Metallic Teal)