I almost think you are pulling my leg, but giving the benefit of the doubt here goes:
On the side of you tc is a "range lever", that is the flat metal piece with a hole in it for the shift rod. When the shift lever is moved in the cabin, the shift rod pulls/pushes the range lever forward or back.
If you have setup the shift lever and shim at the shift gate--fully rearward, then disconnected the shift rod trunion lock bolt so the shift rod is free, you can grab the tc range lever with your hand and shift it through its full range--2wd, 4Hi, N, 4lo. So imagine the shift lever fully forward, and it would have what effect on the range lever, through the shift rod? It would push the range lever towards the rear of the tc. If that is true, then grabbing the range lever and pushing it fully forward should get you 4lo. Once the range lever is in 4lo, and the shift lever in the cabin is still fully rearward and shimmed against the shift gate, tighten the trunnion lock bolt and your done.
Hope that gets you there.