Welcome to the forum. And WOW what a beautiful car. I love that color.

I have been running Dextron ATF in my manual trans 78 240D and it shifts smooth at butter. I had Redline MTL in it for a little while, but I started getting grinding when downshifting even when doing it very gently. Drained the fluid and sprayed it down with brake cleaner, let it sit and dry for a good while. Then filled with ATF. Grinding went away and the shifts have been smooth ever since. And it's got 319k miles on it.

At 75 I hope your engine's screaming, that's nearing top speed for that poor ol' girl. Mine cruises best 60 to 63.

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