Just fitted a used type 9 gearbox and taken it out for a test and there seems to be a problem with 4th. It flicks out of gear and into neutral when I come off the power. Stops in gear when I hold the gear lever. Any ideas or is it scrap. The only thing I've changed is the gear lever. Fitted a quick shift kit.
Cheers Chris.

I wonder if the shift isn't putting it completely into gear? Can you fit a standard gear-lever to see what happens?

too much end float or weak detent springs on the synchro hubs