I broke the pin that goes through the gear to hold it to the shaft. They are fairly strong, as long as it does not more. Mine came out a little bit, almost carved a complete hole line in the top of the tranny. It went flying once it totally broke, no holes in the tranny, but i never found it..

Anyways its pretty strong, i remeber when i broke it, it was the 1ST gear that i broke, i had it at full RPM's spinnig then i shifted it into 2nd, man did that thing ever fly.