well i just bought a 1987 xj with the 4.0 I6 ax15 trans and np231 tcase
and when i put it in first there nothing it doesnt move and the same with every gear so i tried 4wheel and it will move a lil bit in 4 low but wont at all in 4 high or two wheel!! does anyone have an idea of what it could be

 

Hmmmmm...wow.....that really sucks. Its probably not your tranny though, because it did work in 4-lo. It could be something with the rear diff, we need more info. Does it make noises when you try to move, do the rpm's go up when you try to move, etc...

 

well in 4 low if i give it a lil gas it will go slow but not the way it should in 4 low and if i hit the gas hard you will hear it grind and then goes!! and my friend who has worked at ford for 35 years now said he thinks its the transfer case!!

 

Two possibilities come to mind. One is as you already guessed is the transfer case. The second would be that the clutch has been blown and the disc has no lining left on it. Either one is easily checked and confirmed.

 

how would you check them??

 

I would pull the transfer case and the trans to get to the clutch. Once the tranny is out you can see into the bell housing to see if there is any clutch disc left. A hour or hour and a half to determine if both are bad or the transfer case needs a rebuild.
You have to tear into them to find the answers.