Rubding sound

It's a 2000 Ford F150 4x4 with 115000 miles I had this problem fixed before almost a year a go and now the problem is back at a slow speed the sound is louder and the faster I go the sound goes away.

Thanks

Well I was told that the Axle and Hub wheel rubber seals need it to be grease up that they were very dry so they did that and the problem was solved, now almost a year later I have the same problem, and talking to some people (friends) I was told that there is no such as thing as a rubber seals on the axle or hub wheel so by hearing all of that I'm confuse on weather the dealer is telling me something that it's not or it is true and my friends don't know.
Hopefully I answer your question.
Thanks