It is not uncommon for manuals to use Dextron. Chrysler has been doing this as far back as the 60's. Of course the transmission has to be designed for it. The Sikorsky S-76 helicopter also allowed Dextron for some time in its main gearbox. This is essentially a large 1000+ HP manual gearbox that does not shift. I belive Sikorsky no longer allows Dextron due to inconsitancies among oil manufactures, I could be wrong on that. That why you should stick to approved brands. In any case do what your manual says.

John Roncallo