wj3v

2006 FX4 5.4 automatic. When I pull out from a stop and easy with the throttle, I hear a whining noise. You can hear it even when it shifts to second. As the speed increases the noise goes away. When you come to a stop you can hear it again when it shifts to 1st. It only happens when truck is moving. Almost sounds like a grinding noise. I put it up on jack stands and it sounds like its coming from the rear transmission/transfer case area. Truck has 85,000 miles. This started after towing a car trailer with a corvette on trailer about 300 miles. Truck still shifts fine. There have been a couple times when you first put it in drive or reverse it won't move for about 3 or 4 seconds. Anyone have any ideas what this might be? Could it be the transfer case? Thanks...............