I have a 2009 ram 1500 4x4 slt with a 9.25 rear axle. It is making a drone sound which a trusted mechanic is telling me is a rear wheel bearing. So is it one bearing or is there a bearing behind the diff cover and one near the wheel? He mentioned the whole axle slips out and it is a little different than most wheel bearing assemblies. Thanks!

 

the differential case has 2 side bearings, 1 per side (tapered roller bearings). the axles slip through these bearings into the case. the axle is held in the case by a c-clip which allows 1/4" of axle movement in and out. the axle is supported at the outer end of the axle tube by a roller bearing.
hopefully, its the outer wheel bearing and not the case side bearings.