If the noise is coming from the rear of the vehicle, your description could very well be a pinion bearing type of noise in the rear end.
The information I initially sent was the view of the front. I apologize for missing your note of the noise seeming to be from the rear.
The best way to check for that type of a bearing noise, is to hoist the vehicle and put it in gear running it while in the air...then you can listen to it with a stethiscope.
Upon reading your question to begin with, I make the assumption that you were referring to a bearing type of noise in a wheel bearing. And I also assumed that you were referring to a front wheel bearing type of noise.
If the noise seems to be coming from the rear, then you may or may not notice a difference loading the truck by steering side to side while driving.
Although, if there is a rear wheel bearing failing, you may notice a difference.
I sincerely XXXXX XXXXX information I have provided helps in your diagnosis.