My car has always had this washy, slightly grinding, sound coming from the back. The other day my friend grabs the driveshaft where it connects into the rear end and moves it around. There was alot of play. He said it might be going bad. Does the wierd sound support this idea?

 

maybe, maybe not you really need to inspect the internals of the rear to know for sure

 

Your pinion nut could be loose. Does it whine more with or without throttle? Or the same all the time?

 

The faster the car is going, the faster and louder the noise is.

 

The sound is alot like front wheel bearings when they need replaced.

 

it might be the pinion bearing