faint grinding sound from the rear

so sometimes on my 97 4.0L auto 4x4 with the chrysler 8.25 I can hear a faint grinding sound from the rear of the jeep when I am going around 20 mph. It doesn't get worse the faster I go. I was thinking maybe wheel bearing.

check ujoints. actually pull drive shaft and check movement of all joints. check fluid level and condition make sure no metal. you can pull the axle shafts to see if the wheel bearings are ok. check the shaft itself too as the axle acts as the inner race.

My 35 does this right before the carrier disintegrates.

I would start by popping off a rear wheel and looking at the condition of the:

brakes - even a half warn brake shoe can sound bad, or be off kilter, or wear unevenly. Does it pull to either side?
bearings - Luckily they are just regular old school bearings back there, pull the drum, pack the bearing (or replace it) but pack it good.
u-joint - I thought I didn't have any u-joint problems, but was having a "clunk" when taking off or stopping. When I checked my u-joint (rear) I found mangled metal, I was surprised it still worked at all, about an inch of side to side play.