Yeah, I actually replaced it all when I did the rotors. Here's something: Today when I arrived in Vegas, I took the stang to Valvoline as I do with all of my vehicles. I had them check the differential and at 28125 miles it was dark black (obviously bad fluid) and a little bit of metal shavings on the magnet. Nothing too major though. The odd thing is on the ride to the Cosmo to check in, I barely heard the chirping. Sure, maybe it was because I washed it afterwards, but I will know for sure when I leave Vegas on Sunday for Cali. Might be interesting if all this time it was something with the diff.