I recently had my front bearings and alignment done at Les Scwabb. Tires rotated and balanced too. Yet, when I drive my truck, ever so often, there is a sound like when ones drive over the grooved pavement on the freeway. Is that the 4×4 transfer case trying to engage while driving?
You may find that the noise happens more often when slowing down or turning. Noises can be difficult to narrow down. While accelerating or decelerating may be an indication of differential pinion bearings going out. While turning may indicate a hub bearing going out. Have not heard of the 4×4 transfer case trying to engage by itself.