coolrides

Hi, I'm new to working on military transfer cases and need your help.
I have a used T136-27 air shift transfer case.
the pinion nut and washer are missing from the input shaft.
when spinning the input shaft it walks front to back and makes noise.
I will be starting a tear down tomorrow to see if I have bearing damage or gear damage. my first question, does the pinion nut preload the bearings on the input and control the walking motion I am seeing? (kind of like the pinion in a automotive differential) or am I going to be surprised tomorrow and find a junk gear.
If somebody can point me in the right direction to purchase a maintenance or overhaul manual for this transfer case I would appreciate it.
Thanks