Front End Hum between 40 and 60 MPH

Hello all! I'm new to the forum and just recent purchased an '07 Commander 4WD (Rocky Mountain, if that matters). I just installed a 2" lift and am planning on installing Rough Country 1.5" wheel spacers over the weekend. My post is about a front end hum that I get with driving between 40 and 60 MPH. You can start to hear the hum at 40 MPH, it gets loudest at 50 MPH and then tapers off at 60 MPH, not going away completely, but nearly.

The sound is a consistent hum when driving, but the moment you let your foot of the accelerator, it goes away, until you give it gas again. I've been driving it for a couple weeks and the sounds never changes or gets any worse, but it's there and I'm hoping someone on here has run into this will know what the issue might be. I was thinking for replacing the front diff oil, but wasn't sure if that would really do anything. Any help would be appreciated.