transmission or driveshaft groan

[seanman]

so when im decelerating, around 2600 rpms or so to 2000rpms, there is a loud groan coming from what sounds like my transmission, but near the end of it. i was thinking maybe its some part of the driveshaft connection being sloppy and have slack, maybe wiggin out because of it. idk if there is a loose u joint or what. its super obnoxious and i can only guess its horrible for my car. please help my project baby