Update, I removed the nut to find as pointed out by several posts a badly worn "O" ring that was actually missing a small piece. However, there wasn't a spring or ball of any nature behind the nut. I also noticed that both sides of the diaphragm type coupling have this large nut. Perhaps this is a change from some earlier Lippert systems that some folks have had problems with fluid getting into the motors and toasting them. Anyways, 10 minutes and $3 for a package of O rings and I'm good to go. Thanks for all the responses and suggestions!
2011 Georgetown 330TS
RAV4 on MasterTow Dolly