I've had three 240Ds. My first - an '82 automatic - was especially noisy, almost deafening, at highway speeds. My second - an '81 stickshift version - was much better, but still kind-of loud when revved-up.
My latest is fairly quiet and smooth on the road - perhaps because it has a much more solid body and/or tighter engine than my first two.

Anyway, has anyone installed the 3.07 rear-end gear from a NA 300D in a 240D, and can report the results?

Happy Motoring, Mark

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DrDKW