Hi, a few days ago, while driving my 92', some very unpleasant sound emerge from under the car. Whenever I let up the gas pedaal the noise emerge. It sound like metal pieces grinding, or loose inside the transmission housing. I was told that it might be the differential pinion wearing out, any advice on other possible casue?

Oh, I did experience rapid decelation a few times right when I slow down, sounds just like down-shifting.