please dont go and buy a gear stack before inspecting the shift fork. if the fork is bent and u replace the gear stack, guess what?, ur still gonna pop out of gear. gears rarely strip unless u run the tranny dry and heat builds up. the most common reasons for popping out are a bent shift fork, worn blocking rings or gear clutch teeth. worn gear teeth would cause this but that is unlikely because in a transaxle the gears are always in constant mesh. (when u grind gears, its not the gear teeth grinding, its the syncro collar grinding the blocking ring teeth) so check the fork for too much clearance against the synchro collar and check the gap between the blocking ring and the 2nd gear. there should be a gap when the blocking ring is compressed against the 2nd gear. check the blocking ring teeth and 2nd gear dog teeth for wear. check the syncro collar where it slides over the blocking ring and 2nd gear dog teeth for wear.