Eaton Fuller 8LL Splitter not Engaging

Got in the truck today and it is stuck in gear. The shifter is in neutral but the truck is in gear. When I flip the range selector works, I can hear the clunk. But when I toggle the Splitter, I hear the air but nothing else..
I do have some oil in my wet tank , which I will be taking care of in the morning I've heard that can cause the Eaton to get all gunked up inside and cause this. Appreciate any help, ideas or opinons.

BTW, it is in 2001 KW T800 Superdump.

 

SPSauerlnd, I can't thank you enough. I finally got around to getting the shift tower off and reinstalled. It WORKED! It was no easy task, working on it after work every chance I got, through that 6 inch square hole in the floorboard. Everyone I talked to, besides you, were convinced that it was a broken snap ring. That was my mechanics diagnosis as well. That would have cost me round $750 for the tow and the the cost to drop the tranny. I really appreciate that you took the time to answer my post. Thank you again so much.