Ok its about 18 degrees here in missouri. Well i went to put my 04 fx4 in reverse and it made a prety loud noise i think it came from the back. I hope its nothing big. What do you all think? Sorry for lack of info. But thats all i got. Thanks.

 

Unless it becomes a habit, I wouldn't worry much about it. Most likely culprit would be a bad universal joint, unless you have a driveability issue I wouldn't worry about the tranny.