I believe there are several sets of dots on the spedometer, each one marks where the transmission should shift when you start from a dead stop and floor it. Try it out, mine shifts within about 3mph of the dots. (You might not have the dots though, mine is much newer). If they shift in the right spots then your transmission is probably fine.

Old auto trannies can shift really hard sometimes, its just how they are in every car ive driven that had more than about 180k miles on it. One way you can mitigate for it is by easing off the pedal a bit at the right moment to make it shift sooner, if thats what you want I do it all the time in my car, so much so that i dont even think about it anymore. You get used to it.

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1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350