rear end on the moustang

the rear i used to have n my mustang had play like yours does and it made a horrible grinding noise adn many ppl told me the bearins were shot idk how the inside was cause i found a good rear with 373s and junked the old one and put the better one in but mine had the same as yours play like all hell and leaked grease all over my brakes i think the bearings and seals are bad