1999 Mitsubishi Eclipse Strange Noise When Slowing Down

On a couple occasions when my I've driven my car for a while, it'll make this wierd whining noise when I slow down to a stop. it almost sounds like something is rubbing against something else. It seems tobe coming from front of the the passengers side. My friend was driving my car and said that the vibration from the car felt alittle wierd. Someone suggested it could be my differential, but I really don't know. My car is also lowered about an inch and half and is sitting on 18 inch tires, I dont know if this makes a difference but any suggestion as to what this might be would be really appreciated.
thanks
Kim