Keith,

    Man.... I hate to tell you this.... but it ain't got nuthin' to do with
your radiator.  On the front of your auto tranny is a small ovalish heat
exchanger with two hoses attached to this.  I'd bet dollars to donuts that
thing has a small leak between the ATF side and the coolant side.  That's
exactly what happened to mine on my big trip up the Alaska highway.   I think
it was caused by the high heat conditions and my intermittant thermotime
switch.    Not only are you gonna have to replace the heat exchanger... .you
now have to get all that ATF out of your cooling system and then fill and
bleed.   Perhaps the List can give some insight on how to get the ATF out
completely.   Good luck my friend.

Scott De Santi
86 Vanagon 2WD (The Wobbly Bus)
Anchorage, Alaska