don't know what to tell you,....is it getting worse?

my 02 sporty started making a yeernd noise almost like a hydraulic noise today....may only do it every ten miles or so...no idea what it is..does it in 4 and in two with hubs out....my first though was throw out bearing cause it was 0: degrees this morning but still doing it when it warmed up...scary but guess will run till gets worse.....