I have a 1999 Ford Explorer. The problem is while driving the car from time to time I hear a loud spinning noise coming from under the car. The noise sounds like it's spinning very fast. If I give the car gas the sound doesn't change it only stops when I apply the break to almost a full stop. It doesn't fell like the transmission slipping I still have full power. Has anyone had this problem or can give me some direction?

 

Diff bearings, a feature found on many Exploders. Bearing quality is spotty, leading to this kind of failure. Some go forever, some crap out a 50K.

Sounds like the pinion bearing in your case.

Get your wallet out....