Let me start by saying I'm NOT talking about the whiring noise the R gear makes XD When I go backwards (in gear or not) my car makes this wierd noise... almost like the radiator fan is turning on. As soon as I stop going backwards it ends. Any ideas?

 

Also, it doesn't happen all the time. Like tonight it didn't do it all. It does happen when in reverse as well, but also in nuetral.