Move it into diff lock.
That is the center small shifter on the transfer case.

If you have a blown differental on the front and rear or a blown drive shaft,
putting it into diff lock will cause the transfer case to turn each drive shaft - period.

In unlocked diff mode - it equalizes the force given to front vs back.

if you go in locked diff mode then you may have a problem in the transfer case or a blown differential in the front or back.

 

Diff lock is a sideways movement of the lever.
and an orange H light will come on the dash.

 

When I got the car, it had a frozen diff lock, I got that loosened up. The shifter now moves the full range of the opening in the gear change housing. I can see the diff lock move the selector lever on the transfer case, I can't see if it is moving anything inside because I can't get the cover off while it is still on the transmission. The high/low I know is working because I can see it moving the H/L fork, (I have the side cover off the transfer case). Now if the diff lock was not locking in, wouldn't I still have rear wheel drive? As I said earlier, I have both drive shafts moving when in gear, and when it was on jack stands, and tires off, the rotors front and back both move. And they move in the direction that relates to the gear it's in. It just won't move with a load.

The car still rolls free when it's in park, but if I go from drive to park without stopping at neutral for a second or two, I can hear the parking prawl. So my first thought is the trans must be still moving inside because the transfer case is froze in neutral and the transmission isn't stopped like it would be if transfer case was in gear and the car stopped on the ground.
That thought is starting to fade since I got the diff lock moving again.

And now, it seems the trans has no fluid pressure in park at an idle. Not sure were to go now. Maybe, change the fluid and filter and check pressure again. Maybe the parking prawl is just worn out and is a separate issue. Maybe the trans pump is blown or filter clogged. I don't think having a drip in my oil cooler would keep it from showing any pressure, would it?

 

oh, and to add one thing. I don't have any light or sound coming from having the lock on or having the lock in the neutral position.