93 d21 4x4 4cyl no 4th gear

[whitfd27]

Hi I have a 93 d21 4x4 and for some reason it has lost 4th gear. Every other gear is ok but when you put it in fourth gear position it's like it's in neutral. You can feel it lock but nothing happens. I dropped the transmission and took off the transfer case. I put it in fourth gear and spun the input shaft. The output shaft spun freely but when I grabbed the output shaft, it stopped, but the input shaft still spun spun free. Please help!! Any input would be appreciated. Thanks in advance

[PapaSmurf2k3]

Is the transmission still out? I would think you broke a fork or something inside. Sounds like you've got to break it apart, or just swap in a used unit