The bolt on what you call the trunion, is a set screw. It tightens against the rod to keep in in place. This is for adjusting the shift linkage. Once you free the rod to slide back and forth in the trunion, you should be able to move the lever on the t-case. The rod will not come out of the trunion block as it is "pinched" on the end and won't pull through. If you can't move the lever on the T-case, it is probably stuck with corrosion. Unbolt the lever from the T-case and see if the shifter works freely. If not, it's the pivot bolt rusted up. Take the shifter out, take it apart, and clean and grease it up.
Corroded shaft in T-case will require disassembly of the case. Shaft comes out from the inside.