I've been listening to a strange low frequency rumble noise coming from (what sounds like) the engine bay. At first, it was an infrequent noise that was pretty faint and I could only hear it when I put the car in drive. I checked the serpentine belt and there were no cracks--pulleys seemed fine. I could hear the noise inside the car, but for the life of me I couldn't hear it when I stuck my head under the hood (and I mean way under--like my forehead down by the front diff dip stick) to see if I could hear something--anything.
Now, it's gotten louder and I can hear it constantly. When I put the car in park, it's pretty faint, but I can still hear it. When in drive or reverse, it's prominent. When braking, the noise gets louder and then quieter when I come to a full stop. I've stuck my head in the engine again, checked the belt again, etc., and I can't figure out where the noise is.
Could it be the transmission or the front diff?
The car just reached 45K miles and I want to know what the hell is going on. If anyone has any ideas, or if you all need more information, please let me know.
Thanks in advance.