Vintage Minor Register

Can I ask for some help please. I have changed the inside of my 4 speed box three times. I found that 4 speed syncro will not fit into a 4 speed ordinary. I now think I have all the original gears etc in the original 4 speed NON syncro box. All works well EXCEPT on over run the box slips out of gear, mostly at speed, in third and fouth. If I am in third pulling up a hill I keep my hand on the gear lever which stops the jumping out of gear. I do the same in forth when coming up to a roundabout and take the foot off the gas. Reading comments re gearboxes in the last week someone said that there is a difference in the space between the ball and the end of the selector. Could my selector be too short? Could the metal gasket between the lid and gearbox be too thick? I think I have three gearlevers - have these changed over the years? The gearbox works well and is quite silent. Any ideas?

I'd try checking that the gears go fully into mesh in each gear, it may be that the selector forks are not quite in the right place. If this is ok, I'd check the indent springs and balls that push down into little grooves in the selector shafts, sometimes the edges of the indents get warn, sometimes the springs weaken over time. Also your idea about the lever is worth checking, make sure the lever pushes the selectors fully home.
Cheers
Jeremy

Would be interested to know what sorts it out. Have had many landrovers with the problem and they all got progressively worse until it won the test of strength and popped out on overrun no matter how hard you pushed on the lever!( only in the non synchro 1st and 2nd though) My tourer pops out of reverse too and I'm also in the process of removing my mothers Rover 60 box which sometimes pops out of fourth and won't go back in without a fight, the hotter the rover box, the less likely it is to be held in top.
My problem is that I've never got enough to do!!!

I have had problems with more than one Minor' s gearbox locking up if a forward gear was selected when rolling back or vice versa at a junction. The fix is to get out of the car and rock it. This also has the benefit of providing endless mirth for other motorists...