Unbalance drum or washer

i bought some used GE washer and dryer. i’m having problems with the washer…washes well until the spin cycle it vibrates alot and makes a knocking noise. i did level it almost perfect with a good level…i did notice that the rubber on the legs broken up pretty bad. So i ordered some just waiting on them. Could this be the problem? i do see the drum wobbles on slow turns…could it be something else?