1998 Chevy Tahoe Chevy Tahoe noises

I am sorry I have no donation. My 98 tahoe makes a rubbing or kind of soft grinding sound whenever the vehicle is in motion and bouncing up and down. Whenevr The sound is most noticeable at about 10 to 15 miles per hour and when the vehicle os on the down half of the bounce. Have been told different things by different mechs. 1 said it was the front wheel hub assembly. Another said that it was my tranfercase. I just feel like I have no knowledge to protct myself from getting ripped off. If you could please give me some idea as to what it is that im dealing with I will be very gratefull Thank You.