On VW Bugs they used a magnesium transmission case in the 50s. However after Volkswagen solved an engine
oil leak problem as part of a production change they ran into problems with the corrosion that occured due to the lack of
oil mist sprayed over the tranny
At least that's the story I have been told...
I would just spray the case with WD40 from time to time as double ugly recommended.
Simon