Hello and welcome to the MercedesShop. I have never heard of anyone doing this. I do not even know if the transmission would hook properly to the car. I do not know a lot about Mercedes, but I am sure someone here will know the answer to that.
Is there something wrong with your automatic?
I think it would be too costly to do.

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2004 Toyota Sequoia Limited 4wd
1991 Lincoln Town Car Executive
1991 Cadillac Sedan DeVille
1988 Mercedes 300SEL
1972 Chevrolet Caprice Kingswood Estate 9-passenger wagon
1973 Pontiac Grand Ville
(Prior MB's: 1974 240D, 1985 380SE, 1984 190D, 1993 400SEL)