[old_master]

In the early stages of 4WD hub failure, you might not feel any play. The fact that the noise doesn’t change when turning the wheel, indicates it’s probably not the hub assembly. If the noise changes with vehicle speed, it may be from tire wear caused by excessive toe in or toe out on the front wheels. Excessive toe will cause the edge of the tread to become cupped. Run your hand along the tread, if it has a symmetrical "jagged" feel to it, that might be the problem. Applying the brakes causes a weight shift to the front of the vehicle and could explain why the sound changes. The easy way to determine if tire wear is the cause of the noise, rotate the tires front to rear. The noise will be less noticeable when the cupped tires are on the rear. If that improves the noise, you probably need a front end inspection, and a front wheel alignment.