zetor 8145 wont go in reverse

have just put tractor back together after replacing selector shafts and now tractor will not go in reverse

are these adjustable ?? The UR1 5th gear selector was adjustable in length.

Alzet or DaveP would probably have better advice on UR2 tractors...

This is an odd one, I assume its OK with low/high ? I think i'd take the top off the gearbox and make sure the selectors are in line for the left stick and that the detent ball and spring for the reverse rail is ok and that the selector is tight on the selector rail. Failing that I fear you may have to split the tractor in front of the back axle to examine where the low/high and reverse gears are, I have known the needle bearing in the reverse gear to fail making it impossible to engage. Not much help I'm afraid.