I'm at a similar situation where I think I need my tranny rebuilt. Either way mine needs to come out for thr front pump seal, which is leaking. When I first got the car and knew nothing of the vacuum system, I read about the modulator valve and adjusted it WAY soft and drove it that way for several thousand miles. The car had probably 160k on it when did this and a tranny service was done around this time, including draining torque converter.

Eventually I resolved the vacuum leak and adjusted transmission at least close to what it should be. Might I have damaged or worn thr transmission out when I did this?

As the OP is having issues and may have to yank the tranny again, what seals, pistons, or parts are user replaceable without rebuilding the entire trans?

I am thinking may pull mine, install the spring kit and update some of the parts that had known "updates" or replacements. Does anyone have a list of these?

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000