If it leaks from the tail shaft of the transmission it could be the seal (the spring inside the seal could be displaced), the case where the seal goes into, or the yoke that fits onto the output shaft. Possible groove worn into the yoke that fits against the seal. If my memory serves me correctly, A Darrin uses a yoke that bolts to the output shaft. It could also leak at the bolt head that secures the yoke to the output shaft. I can see 4 possible sources of fluid leak.
