Whats my problem?

I have a 2010 6 cyl 4x4 double cab with 98 thou and change miles on it with about 10k miles of towing. Recently there has developed a subtly noise from the front end like a hum. Its only ehn im on the gas and just cruising. Also a slight vibration in the gas pedal. It doesn't seem to be down on power witch leads mw to believe its the alternator or a lose belt. I just changed my trans fluid, air filter, and the bank 2 sensor 1 O2 sensor, after the check engine light came on. All of those repairs didn't help the noise or vibration in the gas pedal. What could it be?

 

Does the vibration go away if you put it in 4WD?

 

10 bucks says no grease has ever been pumped into your u joints..... bad u joints are my guess.

 

Putting it in 4WD doesn't make it go away. The guy at work i go to for all things car related said it could be the u joints. So im going to check those next. Thanks