This past weekend I put an all new 12 bolt and I've noticed that it whines whenever I let off the throttle. It has at maximum 25 miles on it. Is this normal during the break in procedure or is this something to be concerned about?

hey, i just bought a 72 nova and when i bought it the guy said that the rear pinion bearing was going bad and just the other day i saw that the seal was broken and leaking fliud. the car vibrates between like 50-65mph i am going to try the fix myself, although i have never done any rear end...