Auto tranny issues

oK, last night when I got home I went to unhook the CJ from the tow rig. I got it unhooked, locked the front hubs put the t-case in 4 hi (rear drive shaft is out because I flat tow) and parked it on a slight incline, left the t-case engaged, put it in park and the Jeep started to roll and the tranny was making a kind of ratcheting sound, click...click...click. Stepped on the brake, drove it forward again and had my wife put a block under the tire to keep it from rolling. Is this because the tranny isn't fully engaging park (shifter linkage?) or is there some other issue. It is a TH-400 for those that don't know.

 

the ratcheting sound is the parking pawl arm not engaging fully
try checking the linkage; adjust if necc
the same noise is made when you accidently shift into park while still moving (I wouldn't do that )
they can be damaged/broken
here's a pic of the parking pawl arm and linkage; top right is the arm,6.552-1; below is the bracket; they should be cast iron IIRC
I think if repair is needed, you can do this by just dropping the pan.