I don't think there is anything wrong with the car.
An S600 is quite a powerful beast, but it was never supposed to do 220
I just wondered why the engine rpm/wheel rpm was not a straight-line relationship in a given gear.
I guess it must be non-linearities in the torque converter.

Just to run the logic once more, if you are rolling a tyre along a road at 4mph it's going round 52 times a minute.
If you try to roll the same tyre uphill, it's a lot harder, but if you can get it to go round 52 times a minute, you are still doing 4 mph.
Now put a 1:1 motor on it, if the motor goes round 52 times a minute, the tyre will too and it is still doing 4 mph; 104 times a minute, the tyre will be doing 8mph (uphill, downhill or on a road in space). Now add a fixed gear so that the motor has to go round 2.12 times to get the tyre to go round once. If the tyre is going round 52 times a minute, it's doing 4mph and the motor is doing 24.5 revs. 104 times per minute, the motor is doing 49 revs and the tyre is doing 8mph. Motor 3000 revs, tyre 1415 revs, speed 110mph.
So if at 6000 revs of the motor, the tyre is only doing 155mph, the tyre can only be going round at 2015 revs, not 2830 and the only difference must be that a torque converter is not like a fixed gear.

Assume that is the answer, thanks MBZ.
Back to another part of the question, does anyone know a website which carries specs and stats for various MB models?

 

Damn. Too slow on the OK button. That's twice this week.