2013 Tacoma 4wd growling

My truck is pretty new, only 2000 miles on it. We got some snow over the weekend that accumilated pretty quick and alot of streets were unplowed. Put the truck in 4H and everything was fine untill about 30 mph where I stared to hear a growl coming from underneath. It would not happen at speeds under 30 and the sound would go away past 32-33mph upon acceleration. Does this seem normal in a truck this new? A bit off topic but the gas milage sucks too. Im getting a bit under 250 miles on a full tank with mostly city driving. I was expecting about 14-15mpg but not 10-11.

 

Welcome to TW, yes in many cases that harmonic is normal, your instruction on how to operate 4x4 should be on the drivers do, good reference. And give you motor sometime to wear a bit before being concerned with MPG