Same here...I've actually had the diff replaced twice. The first time, they put in the same style diff and the same thing happened again. This was after about 3 attempts at fixing the vent tube, thinking it was that. Needless to say, they found out that the diff was about to go and could have locked up at any time. Get it repaired as soon as you can. A locked diff can be very dangerous if it occurs while you're driving.