It seems intuitive that if you hear weird noises when the car should be shifting, that the transmission is acting up. But would you suspect it if things were going "bump" in neutral? Yes, it could be the transmission.
Such sounds could have a simple and inexpensive solution -- as with many of the problems on our list, adding or replacing the transmission fluid sometimes does the trick. Bear in mind that as is the case with engine oil, different vehicles do best with the specific formulation called for in the owner's manual.
Alternatively, lots of noises from the transmission while it's in neutral could signal something more serious, like mechanical wear that will need the replacement of parts. In this case, common culprits are a worn reverse idler gear or worn bearings, possibly coupled with worn gear teeth [source: Procarcare.com].
Losing control while driving is never a fun experience. Find out on the next page how a bum transmission could have a car "slipping" toward disaster if not repaired in time.