1996 Pathfinder W/Auto Trans- Reverse is gone but all other gears are fine?

[jbo]

My 2WD 1996 With Automatic transmission no longer moves in reverse. About a week ago reverse was real slow then I tapped the gas and the vechicle moved in reverse and all was fine for a few days. I planned an AT fluid and filter change and completed this this Sunday but still no reverse. No weird noises or sounds, it just won't move. Anyone got any suggestions? I hate to go to a transmission shop blind.