Transfer case issue?

I had a.. very interesting issue come up today. I was driving down a dirt mountain road that is nothing more than a sheet of ice this time of year. Approaching an extremely steep incline I put it into 4H. I did this around the same time I reached the dramatic incline and as result accidentally passed 4H and put it into N. The result was it jamming into 4L and losing all gears. I didnt have anything, drive was gone, reverse was gone and I couldnt even put it into park without turning the engine off first. And no matter what I did I couldnt get the truck out of 4L. I got under the truck and tried to shift the linkages myself.. Nope. After some gentle wiggling of the 4 wheel shifter from inside I eventually managed to get it back into 2 wheel (this took quite some time). This resulted in all my gears returning allowing me to leave... This is the same 1998 Jeep Cherokee I restored and put a new engine in this summer. I thoroughly tested the 4 wheel drive after the first snowfall. It works great in 4H but I never pulled the lever past that. So im sure its just an adjustment that needs to be made. How can I fix this issue?

manual or auto?

I would disconnect the lever and see how smooth the t-case shifts with a pair of pliers from under the Jeep (disconnect it at the lever on the trasfer case). If it shifts smooth then your problem is in the linkage, If it doesn't then I would say you have an issue in the transfer case. What transfer case do you have?

if its an auto it sounds like you got the transfer case stuck in neutral. sometimes it can be a pain to get it back into a gear. but its almost impossible unless the transmission is in neutral also. otherwise it can bind up a bit.

"Jamming" it into 4L while moving and in gear is not a good combination. If it's stuck in Neutral, you won't go anywhere, manual OR auto. If you broke something in there to keep it out of 4L and in Neutral you have bigger issues.

The transfer case Low-High-Neutral fork is connected to the input shaft from the transmission and can be difficult to move when there is pressure on it from the powertrain. Usually you need to disengage the transmission first. If its really stuck you might try bouncing between Drive and Reverse a couple of times to unbind it, then put the transmssion into neutral and try shifting the transfer case again after its unloaded