1992 mercedes 300se "w140" with the m104 engine and 722.502 transmission.

I've rebuilt a automatic transmission valve body before in a bmw, it was a Gm6l45 pretty striaght forward, but I also didn't know how to "diagnose" i just bought a complete parts kit and swapped part for part.

Shown below is 2-3 shift piston , and accumulator piston, no idea what any of that is besides it makes the car shift.

My issue was a flair when shifting from 2nd to 3rd, old dead fourms state these seals on these pistons go bad, which I trust since this car sat for 13 years not running, never started or moved.

Now, in my brain, since there is black gunk on those seals, that those seals have effectively shrunk, and no longer contact the bore to provide correct sealing, resulting in low line pressure untill the pressure builds enough to force the piston to overcome the spring. The piston with "no gunk" contacts the the bore correctly resulting in correctly line pressure. Let me know if my assumptions above are on point or not..

Now, I do plan on replacing all the seals on these plastic parts, the car has 93k? And the oil was pretty fucking disgusting, little bit of shimmering in the pan when dropped, no magnet in the pan. "I will add one by the pickup if there is space"

Also, can anyone recommend any good transmission additives for this? I plan to daily it, not beat it but just commute.

In the past I've had great results with lubegard antishudder in a camry transmission and a gm 6l45 transmission out of a bmw for smoothness and shuddering in the toyota

I just want to extend the life of the transmission, and smooth it out, obviously new dextron 3 fluid and filter.

Also that built up clutch debris... in the bmw with 287k on it, there was a little bit of "sludge" if you will i could wipe/polish away, but I feel this debris in the seperator plate is kind of excessive for 93k.. if i have to do a full rebuild i will, just not looking forward to it as I want to get my silvarado off the road for winter.

Thanks guys!