my axle bearings are making a crunching noise but its only at very low speeds? what is going on? i think my back bearings are junk

 

Are you sure its the bearings? If it is then you should be able to hear and feel it in the bearing carrier with the back jacked up and spinning the axle in neutral. Could be grit all up in your chain, making noise.
While you have the rear tires off the ground, see if there is any side to side play with the axle, or if it can wobble up and down. If its all tight, and spins smoothly with no grinding sound or feel, the bearings are okay. The DS bearing are pretty heavy, and should last quite a while if the nut is kept tight and water is kept out of them.

 

well i know the nut it tight and it don't move side 2 side, not sure bout up and down, but i think u may be right with the chain idea