Shuttle Shift on 4341 won't stay in reverse

The shuttle shift in my Zetor 4341 will not stay in reverse. I followed the steps in the Workshop Manual that said to remove the cover on the gearbox cover to tighten a bolt that is in the shifter shaft. I could not find a bolt. I did see a hole in the center of the shifing cylinder and wondered if the bolt had backed out. I need a part number for the bolt or any other suggestions. Thanks,

Hi

If you've taken the "aeroplane" from the top of the gearbox cover, the small lever inside is attached by a small bolt. The part number for this is : 78 147 023.

Mike