I have moved on from the gearbox build and as usual, at the end of the gearbox build i was a confitmed expert and could identify every part, 6 months later i have pretty much forgot it all and would need someone to point out what a gearbox looks like.
i did take pictures and list my own errors in my build thread
Couple of points though . Is it the selector that is not engaging on top or the reverse gear itself? The selector arm engages directly onto the gear and i cant see how this would not slide the gear along the shaft unless the selector mech on the top was not allowing engagement. You should be able to just take off the top covers and slide the reverse gear in and out?