hi there..just had a slight similar prob mine would only go in 3rd 4th if i tried 5th or reverse or 1st 2nd, it would slip back to 3rd 4th neutral position so i looked at the conector rods they were safely attached ok..so then with help from inside car sorted which selector cable was what..then realised that the top of the selector shaft was not moving downwards.. thus it had seized..so ended up taking battery and tray out etc for easier access.finally removed all the selector shaft casting and dismantled it all on kitchen table.. bearing in top of shaft was the problem..ordered one today six quid ..hoping to reassemble in next few days (if yours is similar and you take out the selector casting)..just beware there is a bolt at bottom of shaft that has a common fault on it ,that it may of sheared off..thus the head of bolt will be in bottom of gearbox...then you defo have to split the gearbox casting from engineand try a magnet in too find bolt.. hope this may of been of some interest too you ..best of luck with yours cheers steve