S'up to all!

Just glad I just found this place!
Just purchased a nice Expedition 2 wks ago!
Everything ok except a lil issue when backing out in Reverse, i hear a loud noise like i just hit something and I accelerate but really move back. Other than that the trans is real smoth all the time.

Need some advice before i have it checked.
Im thinking the trans mount but not really sure so help me out.