clydesdale, there may be some hope. Your experience and the results sound nearly identical to mine with my Gen 2 Taurus and its AX4S a few years ago. Lots of ATF
leaked out through a sudden gasket breach (transmission pan or side cover) over the course of a day or two, and I didn't notice until shifting became strange, clunky (especially when pulling away from a stop), etc. It hasn't been the same since, though it got significantly better after I replaced the filter and did a complete pumpout/replace of the ATF
following methods described here on taurusclub (I put in conventional Mercon III instead of synthetic because for my older transmission, Mercon V hadn't yet been fully approved for it).
But the transmission still didn't work as well as I wanted--still some clunking when pulling away from stops, slow shifting and thus slow acceleration, etc.--so after a bunch of research on what I could do short of actual hardware repair ($$), I put a bottle of Lubegard red into the transmission, and the clunking, etc. gradually disappeared, and everything was fine for a little over a year. After that time, the clunking, slow acceleration, etc. began to gradually reappear, so I did another full ATF
pumpout/replace, this time using a Mercon III full synthetic that had just been released, made by Eneos (I was still leery about using Mercon V, but it's been fully approved for these older Ford transmissions since then).
This reduced the returned symptoms somewhat, but not as much as I wanted, so I poured a bottle of Lubegard red into the Eneos, which helped reduce the symptoms a little more, but I still wasn't satisfied, so I tried a bottle of Lucas Transmission Fix. That stuff was so thick that it gummed up the transmission, causing it to fail to shift nearly at all until the engine had revved so high that the alternator fried its voltage regulator and then the battery. So I don't recommend Lucas Transmission Fix, though of course my experience with it has something to do with the condition of my transmission--I didn't expect miracles, but I didn't expect the fried regulator and battery. So I drained about a third of this Lucas-infected ATF
and replaced it with pure Eneos Mercon III (I wanted to see how little it would take to help), and that brought the transmission back into almost acceptable range while I pondered whether to get some transmission repairs done. After driving this way for about another year, I've currently decided to temporarily just do another complete ATF
pumpout/replace, this time using Mercon V, to get rid of the remaining Lucas Transmission Fix. If that doesn't help as much as I want, I'll try another bottle of Lubegard red and see what happens. But during the time between the gasket failure/leak and now, I've been studying off and on about how to do the transmission repair myself, so that's on my agenda at some point in the next year.
My research found some possible candidates for what's failed or become worn in our respective transmissions, with these being some of the more likely possibilities:
• worn clutch discs
• the transmission fluid pump's seal/gasket
• the forward clutch piston
• the Neutral to Drive Accumulator
• a stuck shift solenoid
• a number of other things in the transmission