The seal was no longer an o-ring - more like a square ring; it was
brittle and cracked on removal. The cap was in good shape (never
touched?). Waiting on messing with the trans filter on advice that a
more complete service (cleaning of Control Body) in a good shop would
better serve my needs (I do not have a detailed maintenance history
for the van).

Thanks to all,
Ron Johnson
Portland, OR
'91 Weekender, Betsy