When my Lancer is driving, usually above 40kph, there is a whirring sound coming from the back. What's weirder is that between 40kph and 50kph, it's louder and sounds like it's almost harmonizing with another sound. Once I shift into 4th though, or go fast enough, the noise stops and it's just the whirring noise.

Has anyone else had this issue? Or does anyone even understand what I'm saying?

 

1. Could be rear bearings.
2. Could be rear tires.