I think you are right that this happens TriX5. I'm sure people get advice to have transmission work done and decide just to unload the car. I know I considered it briefly when mine started to exhibit symptoms.

I think people also try replacing half their ATF and then add in another fluid of different viscosity. This likely isn't very good for a transmission. To replace all the fluid, you have remove the transmission and drain the torque converter. As we know this is no small task.

My particular problem was a very slow oil leak at the bell housing. It was just accumulating underneath the transmission oil pan and there was no fluid hitting my garage floor, so I wasn't too worried about it. Then one day when it was cold, the torque converter didn't want to lock up for about 10 seconds. I was giving more throttle and the engine just revved higher with no acceleration. Then it locked up and I drove home.

I did some reading and figured out this symptom is consistent with a torque converter seal leak and a gradual decline in the ATF level. At some point, the torque converter won't look up consistently if the fluid is too low.

I almost have the transmission out. I plan to inspect the debris in the oil pan and filter plus drain the torque converter. If there is anything more than just the usual shavings around the magnets, I will likely decide to do a full rebuild. For now, I'll cross my fingers ...

Anyway, my point is I must not be the only one with this very slow ATF leak. With no easy way to check the fluid level and no scheduled maintenance of the ATF, most people would be unaware of the issue. And if the symptoms are ignored, eventually the torque converter would self destruct and spew bits of metal into the transmission.

Progress
 

Re-assembled the output section with the new bearing. Then I disassembled the F-clutch but nothing to report. The seal seems to be an integral part of the "piston", no replacemnt for it in the overhaul kit.

I used special tool DWV-001 :-) Using my drill press and a magnet I could get the half rings out.

The F-clutch section is back in the housing, more tomorrow.

I've been using this stuff. Back of the bottle lists compatible types.

I like Mobil 1 products in general. However, that Multi-Vehicle fluid is only certified for Ford/Mercury vehicles (Mercon V), and Allison C4 (medium duty truck). Doesn't meet any other manufacturer approval standards according to the Mobil 1 site. It is also a blend, not a full synthetic, if that is important.

Bell housing is back on!
 

A day well spent, got the C, D, and E clutches together and popped them in to the housing. Then put the V-Pan and rear manifold on the motor.

Once the wife came home she gave me hand with the A and B pistons as the circlips on them are harder to remove and I didn't really have the right mandrels either.

Then torqued up the pump and put the whole deal together!

Looks like rain tomorrow so with a bit of luck I should be able to get the valve block reinstalled and attached the TCase, maybe even get it reattached to the motor.

BTW, I found one O-ring in the E clutch piston was sheared in 2 places. I am fairly certain this happened after the TC went south based on my wife's report of a hick-up while driving it.

She is ready to but put on the motor
 

Yesterday did not get much done but today reassembled the unit and the TC.

Ofcourse the first time I tightened the valve block I forgot to engage the selector, aaargh! When re-read the manual it dawned on me that despite remebering earlier, in the end I forgot. So off it came.....

I put wheels on the skid so now I can just wheel it under and jack it up.

Still have to attach the oil return hoses from the EGR and OSV before the AT goes in.

Oil return hoses are on.

Changed the fuel filter, yuk, what a stupid job. I wonder if it is not easier to drill out the rivets and just take the aluminum shield down.

I am ready to put the AT back on :-)

You are almost done. Congrats, great job!
I am not sure if I will do it when time comes but I am pretty sure you enjoyed the challenge. How much was the cost for all this?

Home for 20 hours! Last night tightened the drive shafts, the rear frame and all the bell housing bolts as well as the attaching the TQ Conv to the flex disk. Put the wiring loom back.

This morning put the water hoses on the rear manifold and put the intake back on. Everything is back on the top of the engine, just need to do the fan clutch.

When I get back need to install the oil lines and the heat shields.