In overdrive and 3,000 rpm. How fast is that?

The final drive ratios are different between AW-70 and M46/M47, but the AW-70 has a taller overdrive ratio to compensate for the difference. Hence, normally aspirated 240s cruise at 80 at 3,000 rpm in top gear, and turbos do about 75.

Both my previous 86 sedan (AW70 auto) and my current 87 sedan (M47 manual) indicated nearly 80 mph at 3000 rpm in the highest gear.
My wife's 82 245T (M46 4spd+OD) shows a little less than 75 at that rpm. And even with a new speedo cable, it seems flaky. The electronic speedos are much more stable.
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Rob Bareiss, New London CT ::: Roterande Fläkt Och Drivremmar!

With an automatic (AW70) on a 1984 non-turbo sedan, about (very roughly) 70 mph as indicated on the speedometer (not necessarily actual speed -- see below).

But that varies with year (gearing), turbo or not (gearing), and sedan or wagon (different gears AND different tire diameter), hence my qualifications of my particular car.

Also, with an automatic, it will also vary with throttle setting (accelerating or not) and whether you're going uphill or downhill -- the torque converter allows this). I've got a tach on my '84, and its interesting to see the variation in rpm (a couple of hundred, plus or minus).

But 70 mph is in the ballpark per indication on your speedometer, which is strictly driven by your drivetrain (from tranny up to '85, or your differential '86-on).

AND ALSO just in case: if you're trying to use your tachometer in place of a speedometer to avoid speeding tickets, all of the above is also affected by your aftermarket tires! Don't forget that.