Lost reverse only in transmission.Made growling noise at about 65 mph.see detail

What is your question?

Driving interstate, major growling noise like rear end going. Got to the house no reverse. Could this possibly be an electrical issue. I had recently pulled transmission out from the motor just enough to replace freeze plug. When I pull it into reverse I get nothing, no weird noises, no surges, nothing. Oh yea van is used for ice cream business.