Help on jumping reverse gear

[simbad]

Chaps,
Any help appreciated.
I am helping my son get his first mini (86 mayfair) on the road. After getting most things working have found it jumps out of reverse gear. Is this simple to resolve or do we have a bigger problem.

[rww]

I had similiar problems with 1300 Metro. Centre mainshaft bearing had collapsed causing severe noise. Rebuilt the gearbox with new bearings and on completion found that it jumped out of first and reverse, especially at throttle lift off. From memory,these two gears share the same selector fork
(1st & 2nd) and when I changed this all was OK.

Is it just reverse gear or can you get it to jump out of first also?

[simbad]

Thanks for help.
Its only been up and down the drive, so as far as i know its only in reverse gear. If you hold the gear stick it stays in.
I hope i dont have to take out engine and gearbox

[Cooperman]

Try taking the RH drive output cover plate off Just drain down the oil and pull the shaft out. There is a small spring, retained by the cover, which presses onto the gear linkage. If you stretch the spring a bit, or put a couple of small washers behind it to increase the spring loading (or, better still, get a stronger spring) it may, just may, cure the problem completely. I had a 1990 Cooper 1275 which did exactly this after the box was rebuilt and I feared having to do another rebuild. However, the 'tweek' of the spring provided a complete cure.
Good luck with this.