Based on my "limited time" research....
The Freestar mini-van comes with a built in ATF cooler (build into the main rad). This cooler is for normal driving / NO towing conditions. With this in mind, an "additional" ATF cooler must be installed for towing &/or heavy hauling. And, installed "in-line" with the factory's main rad's built-in ATF cooler - to ensure ATF is quickly heated up at initial start up.
Note about Ford mini-van transmissions:
"Freestar/Montery has much better drivetrain. Windstar uses basic drivetrain as Taurus. Freestar/Montery uses a transverse mounted version of the same V6 used in the F150 truck & E150 van - which is much better for towing. "
The Freestar mini-van can tow up to 3,500 lbs. Some say up to 3,800 lbs - depending on the exact year and driving conditions. Their factory transmission is better than previous Winstar transmissions but like all mini-vans, cannot take "high heat". Heat kills all transmissions. If towing (even a little PUP or utility trailer), an additional ATF cooler should be installed. In my books, that means "must" be installed.
IMO, the LPD (Low Pressure Drop) aux ATF transmissions are the best. Good brands are Tru-Cool or Hayden. Many say that Tru-Cool brand is the best. For sizing, I'd recommend the install of aux cooler rated for 5,000 lbs trailer. Especially if you travel in hotter temp regions or in hilly regions. For example: http://www.transmissioncoolers.us/Me...ansaver-cooler
How to install ATF aux Cooler (sucking it against existing AC rad): http://www.ehow.com/how_5630882_inst...-freestar.html
If living in colder region (like me), I'd recommend installing the ATF aux cooler on vertical steel rails approx 1.5" "away" from the front AC rad. During winter months (when temps are below freezing), simply wrap a thick winter plastic bag around the ATF cooler. When hotter spring months finally come, simply remove this outer water resistant bag. Think of this outer bag as a thick winter coat - to stop its internal ATF from getting too cold during the harsh winter months. To view the ATF aux cooler on my mini-van, surf:
Winter time: http://i178.photobucket.com/albums/w...interRAD-2.jpg
Summer time: http://i178.photobucket.com/albums/w...ummerRAD-2.jpg
Vertical support rail gap: http://i178.photobucket.com/albums/w...rSupport-2.jpg
Note: If installing 1-1.5" gap away from AC rad, always install 1 size larger. For example, install aux cooler for 5,000 lbs trailer (instead of needed 3,500 lbs trailer). When gaping is used between different rad layers, larger size ATF aux cooler is better.
Always remember the more weight one puts inside the Tow Vehicle, the less weight is allowed on the trailer. For example, if 500 lbs of passengers & cargo in the mini-van, then max weight of connected trailer is really 3,500 - 500 lbs = 3,000 lbs. Many folks forget about subtracting the internal cargo weight of the Tow Vehicle.
If your Tow Vehicle's automatic transmission "hunts" for 3rd (D) gear too much, manually put the shifter on D, and slow down. Especially when fighting a head wind or climbing up steep hills. A transmission runs much better at higher RPMs compared to "stress & high heat" of its lower RPMs. With my mini-van, it pulls nice in "double D". Only need to manually force it into "D" when climbing up the steep Kingston hills.
Also remember that "towing stress" (like hills, wind, stop/go traffic, wind drag from attached trailer) is very hard on the Tow Vehicle as well. The more "stresses", the increased risk of mechanical problems. For example, buring out transmission or front bearings. Unknown to some, a loaded 3,000 lbs utility trailer pulls much easier (less wind drag) than a flat frontal design 3,000 lbs Travel Trailer (even though both items are of same equal scale weight).
IMO, any trailer weight 1,500+ lbs connected to a mini-van needs "brakes on the trailer". Electric trailer brakes are the best (compared to surge brakes). With mini-vans, do ensure your attached trailer has brakes.
As with any brand of mini-van towing anything, drive it slow and steady
. Especially when climbing up hills or fighting a head wind. The gentler you treat your mini-van (while towing), the more it will thank you in return....
Hope these items help....