I've got a 4850 MFWD tractor with a powershift that Iam always a little hypersensitive about when I comes to the transmission.  I've heard the horror stories of how expensive they are to fix.  Anyways, I've got a dozer blade on the front and was using it to clean some trees up yesterday.  I bent down near the rear tire/axle yesterday to pick up some limbs, and heard a growl type sound transmitting down the rear axle shaft.  I went around the other side and heard it from that axle shaft as well.  I never heard the noise before, but also never really made a point of checking for it, just kind of happened upon it.  This was with the tractor in parked, at idle.  And the noise when I put my ear to the end of the axle shaft sounded to me like a dry bearing type noise.  Is this normal, something to be concerned about, something I should take to the dealer for further inspection?
Forgot to add: It's got about 11000 hours on it and did have a fairly extensive tranny rebuild before we bought it about 3 years ago.
Thanks