Although I am learing from experience and this forum that all sorts of vacuum leaks can cause hard shifts, I have recently found another vacuum leak/cause of hard shifts that is easy to diagnose. I have an 85 300TD.

During the summer when the weather was warmer, I was experiencing intermittent hard shifting combined with slow engine shut off. Haven't had any trouble all winter. The other day, for the first time in many months, it was warm enough I wanted to use the center air vents. AS soon as I punched the center vent button on the climate control, I had immediate hard shifting and slow shut off, and no air to speak of coming out of the center vent. I'm fairly certain it a leaking vacuum pod for the center vents. Probably have a problem with floor vents too, since I don't have much heat down there.

The entire egr and arv circuits on my car have been deleted.

It's simple to check whether the climate control is the/a culprit on my car, an 85 300TD (same climate control as yours, I think) If I take off from one stop light with either the defrost or defrost vent and floor (the two left buttons) it shifts as it should. The next stop light, if I push either button for center vents, it shifts very hard.

Might be worth the simple test.