We have a '94 (4x4) with a nv4500 that all of a sudden lost reverse - only reverse. When we pulled the tranny and put it in reverse it appears to be in gear -input and output shafts turn as they should. All forward gears work fine. It acted as if it was in neutral but it was in reverse...no bad noises... Shift forks appear fine.

any ideas to chase?

 

It turns out the shifting fork in the transfer case was so worn (only 1/16 of an inch left) that it would not engage in reverse for some reason - still made things work in forward gears... only time, money and new parts were in the road!