I don't know if it is any help, but Monroe came out with a load type of replacement shock for the rear of the windstar.
It is their "sensa trak" shock, with a load bearing spring on it.
They sell them at
www.rockauto.com and they have a link to a picture of it.
The price stated is for 2 of them.
As phil stated, a tranny cooler is a MUST, as is regular fluid changing.