<VV> Tranny input seal

[Cliff Tibbitts]

Well, last week, I replaced all the seals and gaskets on my 66/differential
and 4 speed tranny.  I coated the input shaft seal and lip area with grease.
I bolted the diff and tranny to the now complete engine.  I filled it with
Synthetic 75w-90w gear oil.  I left for a week and returned to find a puddle
about 6-8 inches in diameter.  It is definitely leaking around the "New"
input shaft seal.  

Is it likely to seal up eventually?  Could it be due to the synthetic oil?
Other thoughts or suggestions?

Thanks, 
Cliff Tibbitts
Lexington, KY