I get a deep whine/ rumble that appears to be coming from the back of the car. It has started recently and only makes the noise after having driven the car for about 20mins as if its caused by something warming up.

Its a MY93 WRX and when i first heard the noise i assumed diff so i changed the fluid as i wasnt sure what condition it would be in. It seemed fairly clean for a diff. the noise is still happens now that the fluid has been changed. I may have put too much fluid in??? could this cause this noise?? also the noise disappears when going around a right hand bend but is still there when going around a left hand bend.

other possible reasons i have found could be wheel bearing or dodgy tyre. i must say i have one new tyre on the drivers side rear and a fairly old one on the passenger side rear.

any answers or help would be nice, cheers.

Gaz