Hi names Wes
I have a 1989 Cherokee 4-door with the inline six and the np231 trans case. I don't know a great deal and have read so many threads. I lost my forward gears in my jeep I have reverse, park, neutral, but no drive. I have replaced the tps, the Nss, all the lines for the trans fluid and all.

 

What was the color/smell of the trans fluid. Was it up to the correct level? I would start with these two.

 

Sounds like you need a transmission.