And finally, one thing I've found to cause major leaks is the housing for the speedometer cable driven gear. I know it's a long way from the dust cover, but the inner housing (known as the "bullet") has an o-ring on the outside but can wear an egg-shaped opening inside. This can cause all sorts of leakage.
If I understand things correctly, the "early" parts (I have no idea what year range) were made of pot metal, but later replacement parts were made from steel, which had less of a tendency to wear internally.
Good luck with it...if you replace everything that's been mentioned in this thread, all you'd need is some new clutch packs and you'd have a brand new tranny.
Ray
