I bought a recently rebuilt (3months ago) T-5 from a guy who said the 5th gear was out. Pulling the tail shaft revealed the snap ring and 5th gear had slipped down the output shaft. I pressed the gear back into position, and relocated the snap ring into the groove. Within 10 miles, (never even using 5th gear), the gear slid back down the shaft. The gear is a tight press, and the snap ring seems to fit in the groove. What gives? Did the previous rebuilder make a grevious error? Please help as pulling the trans is getting pretty old.