4 speed gearbox

[topknot]

Hi there, the gearbox has started to jump out of gear in top when on over-run going down hill..
any ideas what is wrong?
peter

[MarkyB]

There is a small chance it isn't engaging properly, a much larger chance that the box needs replacing or reconditioning

[bmcecosse]

If it was working ok before - and now it's doing this - the end is nigh.............. Start looking for another box, or slip it in to neutral and drift down the hill. DO NOT attempt to 'hold it in' with the gear lever - you only compound the problem by so doing.