So I have a 2011 Mustang GT. It has 91xxx miles as it sits. So I only got the car about 4 months ago and recently I started to hear a howl that seems to be coming from the differential. As far as I know, the car came with a 3.31 and was later switched to a 3.73 Ford Racing ring and pinion. The noise only started happening since it started getting colder (50F) and only does it for the first mile or so on cold mornings. Im hoping its just the fluid taking a bit to warm up but im not sure.