I don't have a 410 but what you are experiencing is definitely not correct. My 404 runs 63 mph at 3000 rpm. According to this site you should be about 78 mph at 3000 rpm in top gear, and 90 mph at 5000 rpm in 2nd gear.
Specs 1991 BMW 850i automatic
Other posters have already given advice on some possible problems (calibration of tachometer, not shifting into top gear....). Another might be slippage, either in the torque converter or the ring gear brake bands in the gearbox (but I expect that you would be able to smell the overheating).
In any case, I would have this checked right away.