Any up and down and forward to back means your bearings are bad and need replaced. easy to replace as long as they are not frozen in place. while your at it put in a grease zert. extremly cheap and will prolong your bearings, which save you money. Now if you would of only had side to side movement and none forward to back and up and down then it would of just been your axle nuts. which are the 2 big nuts on your axle by the sprocket.