I'll jump in here and muddy the water a little more. I use the Chrysler spec ATF+3 fluid in my MTX75 and it works great. ATF+3 has more friction modifier than Mercon so it is a little like getting the cocktail without the hassle of mixing it. I haven't been using synthetic ATF+3 though, partly because I have not been able to find it and partly because I don't want to be so proud of it that I won't change it from time to time. If I lived in a colder climate I would most assuridly look for a synthetic version of ATF+3. Before I tried ATF+3, I would change the Mercon every 15,000 miles. I would see some improvement for a while but it wasn't long before it was shifting in a "notchy" manner again. With the ATF+3 the shift quality never drops off, but I still change it every 30,000 miles. THE DIFFERENCE IN SHIFT QUALITY IS ABSOLUTELY AMAZING. If it does not fully resolve the cold weather hard to shift into reverse problem it is still more than worth it. One of the Cougar owners (I think it was Dan Beggs) says that the ATF+3 works better than the Mobil 1 cocktail in his car.
As far as voiding the warranty from using a fluid other than what Ford specifies, that is true, it could, even if what you put in provides the same protection. As long as the car did not come with the latest honey colored factory synthetic fluid, I don't know how they would ever know. Red transmission fluid all looks pretty much the same. I have never know of a dealer sending the fluid to a lab for identification.
For those that do have a car new enough to have been built with the new honey colored fluid, it would probably benefit from adding the 2 oz of friction modifier. As far as I know, no one has tried it yet. I doubt that anyone would know that it was added to cause a warranty problem.
About two years ago I found a Special Service Message on OASIS about the shift quality problems with MTX75 transmissions. It had a phone number to call and talk directly with an engineer. That Special Service Message no longer comes up. I think the engineers name was Terry. We had a good half hour discussion about the MTX75 and their problems.
The cold shift into 1st and reverse problem could have many root causes. He would help guide a technician through the problems to determine how to overcome it. In some cases it was a clutch hydraulic linkage problem and he would arrange to ship a new clutch master and slave cylinders if bleeding the clutch did not resolve it. He said that he was never told what the difference in the parts were, but that they were different than would you would get through normal channels.
In some cases, he would determine that the problem was internal to the trans and he would arraange to ship the new design trans with changes to 1st and reverse. These latest model transmissions only hold about 2.2 quarts of fluid instead of 2.7 due to the modifications. From what I've read here in the forums, this new design did not always solve the problem either.
It was his opinion that the friction modifier had no effect on the cold shift problem, that the friction modifier had no effect until the trans was somewhat warm, something like 70 degrees if I remember correctly. My obversation does not agree with this. I must say though that it seldom gets down to freezing here in southern California where my car is driven.
It was his claim that the european Ford vehicles that used this trans also never used GL-4 fluid, rather that they always used ATF. This is in conflict to research made by Ray McNary. Ray reported that his sources said that GL-4 was used in Europe. The engineer was not sure if they always used Mercon. It is possible that for the first year or two or three that they used type F.
He said that the Focus MTX75 was the same transmission as the Contour except for a different case. To make everything fit properly into the Focus platform, the main gearbox was at a slightly different angle, making the transmissions not interchangable although everything inside the case was interchangable.
One last thing about the MTX75 from Ray McNary's research. All of the transmissions built for US use had a two pinion differential in the final drive. There is a european application for that trans that uses a much stronger four pinion differential. He was never able to find a source for the parts. The most common method of improving the strength of the final drive has been to install the Quaffe LSD which also provides the benefit of limited slip as well as extra strength.
Like I said, this will probably muddy the water.
