I have a Dodge Ram 1500 4wd and it started making noise on my driver rear wheel like crunching marbles inside my rear wheel assembly inside the rim. What could it be?

 

I would suggest that if its coming from the wheel, it might be a broken brake hold down or return spring inside your drum. If thats not it, its possible that your outer axle bearing has destroyed itself from its race and the bearings are clanging around, either way I would check it immediately. You could get a broken c-clip from the axle and your whole tire axle assembley will come out, or if its the brake problem, a loss of that brake, or lock up. Either wat NOT SAFE.