Classic/Antique Car Repair: transmission leak, drain bolt, seal failure

Question
What would cause a transmission to leak suddenly , I have a 1968 Camero?

Answer
1. car wreck
2. overfilling
3. bolt missing
4. bolts loose
5. front seal failure
6. filling tube failure
7. vacuum assist solenoid failure
8. hole in vacuum tube
9. rear seal failure
10. pan drain bolt gasket leak
11. Torque converter weld failure
12. torque converter blade breakage
13. Radiator internal tube cooler leak
14. Body housing crack
15. cooling lines hole
16. cooling lines fitting leak
17. vent hole overfill and/or overpressure
18. overheating
19. bullet hole
20. vandelism

Perhaps if you were a little more specific in your question, I could be a little more helpful.