This doesn't sound like a stripped gear to me. My climax had this problem a while back and I found that the universal joint connecting to the central gearbox (part 25706) had split. This meant that the one of the trucks was only driven by friction on this join. When I glued it back on I found it has worked fine ever since.
I would suggest unscrewing the pan under the driving wheels and take a look.
Hope this helps.
Max
I would suggest unscrewing the pan under the driving wheels and take a look.
Hope this helps.
Max