Variator in 4 gear aut?

Hi, I recall reading somewhere that the automatic 4 gear (the 4th gear) has a sort of variator like in a scooter - is this right? Ie. the more speed the
higher the gear goes in 4th gear. Any ideas on this? My car is 190 D 2.5 4 gear aut. 1987.
Regards Niels Ulrik

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