stuck in reverse

Hi to all help needed was driving my 1986 2.5 na diesel 90 home the other day came to the gate droped from 5th to 4 to 3rd then tried to go to second but it wouldnt go into gear tried to go back into third but the lever wouldnt budge. so i stopped and discovered that i was now in reverse and it wont budge out of gear i have rocked and shoved and pushed and pulled. I thought i had a wound up gearbox so drove it in reverse for a bit but to no avail. Any ideas i have a spare box in another defender but if i can get away with i dont want to go through the hassle any ideas i took the seatbox out and tool the top off of the box hopeing it Might be just a siezed lever but no. Any ideas?..

dont know if you have the same box as me...but this has happened a few times to me... only once in reverse though... peel the gaitor up at the bottom of the gearlever.. where the lever attatches to the shaft.. fish around in the grease.... there is a small grubscrew.. on mine it works loose it holds the lever tight on the shaft.... so all that happens is the lever slides up the shaft without moving anything... once it fell out an i had to fish around for ages lookin for the grubscrew.. i