Went for first ride in my cuda to gas pumps and easy driving around city. When I slowed down to turn into back alley for garage I noticed a noise in drivetrain only going slow. Driving into garage and backing up slow either direction I would here a grind like unjoint bearing or diff. Tried backing up slow and took it out of reverse and let clutch out. Still have this intermitent noise. I removed driveshaft and checked bearings. They were fine and gave them a shot of grease anyway. Everything on this car is new. Any ideas??