The factory heat exchanges for the ZF that are bolted to the side of the bock are known to fail causing failure to the mecanatroinics (spelling?) unit in the ZF when water is mixed in there and the ZF becoming totally stuffed, there are quotes of there of around the 3-4k mark to get it rebuilt.
There are many theory's on why this happens some say it is due to electrolysis and the electronics are trying to ground them selves through the water system and eating through the aluminum of the heat ex-changer, causing the leak and mixing of the ZF fluid and Coolant, Others say it is due to the casting sand getting caught up in the tiny fins of the heat ex-changer and causing it to rot out. There is also talk of vibrations causing the fragile units to fail.
Over on AFF there is a few cases where people have replaced them and only to have them go again in a matter of months. Hence why i believe it is the electrolysis theory as they are known to have poor battery circuits the can cause gremlins and it will eat through aluminum very quickly. I know Bluepower suggest to customers to put a second earth strap from the engines. There was a bit of hype over on AFF about the milkshake problem not long ago and a few company's started making replacement units or alternative systems.
PWR make a replacement system using the same theory of a heat exchange type. It is not placed in the same position but further back toward the ZF, there system is said to heat the ZF to optimum temperature fast and also being a higher quality unit wont cause failure as it is away from he vibrations of the engine. IMO this is just like replacing the stock issue poor design with another.
I chose to replace mine with an independent system that does't connect to the cooling system at all, It has a stand alone Cooler at the front drivers side of the car with a Thermo fan attached to cool if necessary. This system is built by Furious performance who had been putting them on Taxi's for a few years they are a sponsor on AFF and couldn't recommend them any higher. Now there is talk that this system wont heat the auto up quick enough and will cause issues, however I've had this style system on for 4-5 months now and its is exactly the same as it always has been and I don't have that feeling in the back of my mind thinking could it fail and cause a milkshake is it ok?? etc.
This only applys to the 6cyl and the V8's have another style system in the V of the engine block. But again it is still know to fail.
All these systems aren't cheap around the $800 mark, but much cheaper than a trans rebuild. The problem with the Turbo cars is that simply fitting a cooler in front doesn't work as there is no room as the inter-cooler, radiator and condenser are all up front. they have to be fitted in the driver side behind the fog light.
Remember that you need to service the ZF at the same time too that is around the $600 mark and make sure you use genuine ZF lifeguard fluid. Ford want to charge $95 a ltr for this stuff. Also make sure your transmission specialist has done one a few ZF's before are they have a very specific way of checking the level's and servicing.
Here are some (bad) pictures of my set up. I went all out and got braided lines and fittings to match.
Shoot us a PM if you want anymore info.
