Edward, thank you for the tip.  I checked the oil level after coming back
from church.  The van was slightly tilited to the right, and about 12
ounces of oil came out.  It looked like a dirty version of 80/90 gear oil. 
I turned the van around and used a old turkey baster to put a pint of fresh
80/90 back in.

There was a thin covering of ATF on the transmission pan and the final
drive housing.  While working under the van, I noticed a couple of drops
come from the back left cover of the pan.  I got about 1/8-turn on each of
the back nuts.

In any case, the mystery of the 3 quarts of ATF continues.  I am not sure
what 3 quarts of ATF in 20 quarts of coolant would look like.  I partially
flsuhed the system before putting about 250 miles on the van yesterday and
also cleaned the overflow tank.  The overflow tank looked clean this
afternoon.

Any ideas would be appreciated.

John Lauterbach
Macon, GA
'84 7-passenger