John,
Sounds like you removed the plug up high on the side of the final
drive?  Unless it was really tilted, 12 oz sounds like a lot.  But then it
doesn't explain your missing 3 quarts.  Those drips        sound like maybe
the source.  I replaced the filter and gasket on my 86, and remember having
some trouble getting the pan back on with the gasket in properly.  Seems
like at first, all looked good, but the oil ran out as soon as I put it
in.  Or leaked at a surprising rate anyway...  That might be your
problem.  I would think 3 quarts of atf in the coolant would be
noticeable.  Is your coolant level rising?  Also, I would think the leak
would go both ways.  When you first start it up cold, the pressure in the
atf side of the cooler is higher.  When you shut it down hot, pressure
would be higher on the coolant side.  I think you would know it if much
coolant at all got in the atf.  Both by appearance and performance.
Edward

At 10/27/02 04:08 PM, you wrote:
>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