Transfer Question

My transfer case is extremely hard to get into 4 high. What problem(s) do I need to be looking for. Currently I am doing a frame-up restoration and have the transfer case removed.

OK, first question. Is it a J-shift ('73 to '77 where the shift pattern is revers "J"), ir is it a T-shift ('66 to '73 where the shifter handle looks like a big "T" except the '66 and it only moves forward and back)

I have an early model 73 that has the old style t-shifter.

OK, T-shift I know.
Shifter bushings. Those get sloppy.
The shifter lock plate may be out of adjustment (and/or bushings) hitting the end of the travel in the lockplate before you get into 4HI
Body lift/trans swap will often leave the shifter in the wrong place and the hole in the body doesn't give clearance for the shifter.

You should note that the D20 is an all gear non-synco transfer case. Nothing you can do to it will change that. Being so it has an issue shifting into and out of 4WD (both high and low range) where if the gears inside are not lined up, it doesn't want to go into 4WD and if there is pressure on the gears (bound front to rear) it won't want to shift out of 4WD. When that happens just give firm steady pressure on the shifter and drive slowly. Sometimes when shifting out of 4WD you may need to stop and reverse direction while holding pressure. My preference if rolling is to shift out by holding pressure and giving a little "blip" of the throttle. That is enough to unload the bind and shift into 2WD (high or low) then get to where I want to be.

I know that being a gear driven transfer case that shifting into and out of the different drive combinations is more difficult than the newer syncronized transfers. The shifter is almost brand new in that it has less than 1000 miles on it since it was replaced. My main thoughts and concerns here where that since I had things torn down if there was any internal parts I should be looking at now is the time for me to replace them.