Gearboxes

["Slack Alice" Simon]

John D, in the "What have you done today....." thread, says his gearbox "imploded"

If you read this, John, what happened?


And as a general question, what is most likely to go wrong with a gearbox?

I'm asking because I would like to know what trouble I might expect on the Russia - Japan trip.

Generally, gearboxes in normal use seem to go on forever.

I'm asking about 4 speed boxes in particular.   

I think I know that selector springs can weaken or break, and gear levers snap.

What else?

Thanks

Simon