Wanted T25 2 litre aircooled gearbox

The subject line pretty much says it all, obviously it is the engine that is aircooled - well I suppose that the gearbox is aircooled too! A CU engine code; 4 speed gearbox. My box packed in on the way to Newcastle on Friday evening - we were hoping that it was a clutch failure! Any advice or information would be appreciated, Cheers, Bob.