eclivic

I have a 99 Sierra with Pull Shift 4 Wheel Drive not Button so I cant seem to find any help searching this or any other forums. I blew a Tranny line 3 weeks ago so I am swapping in a rebuilt tranny and I figured since I will be under there maybe I can fix the 4x4 issue. Basically what happens is if I go into 4 High and then go to 2 High, The 4x4 light shuts off but it doesn't disengage. When you drive say 100 feet or so something slams and it finally disengages. I have read a bunch of stuff but cant seem to get any help because everything I read say push this button and that button but I don't have buttons, I have a stick that I pull back and forth. If im in 4 High then switch to 2 High and go into reverse about 5 feet it will disengage but that does me no good if im driving on a busy street and need to get out of 4 High.