Finally getting to this. The side pan was leaking fairly bad, super annoying. I marked a line on the linkage brackets, there are 2 you have to remove, then the side pan comes right off. The linkage shaft is sealed from behind by a big rubber washer (that was not leaking). I decided to clean the pans with a hard sponge type grinding wheel. Primer and paint, used VHT aluminum ( prob not factory correct). Found gaskets and seal kit on ebay, installing later today. Five of the side pan bolts have copper washers that go on the lower half. Looks like all the factory bolts were still there!

 

Got it back together, will add fluid and test tomorrow. Not taking any chances, using a thin coat of Aviation Petmatex.

 

That trans looks pretty clean inside for something almost 70 years old.
I'm sure it will serve you well into the future.

 

That's excellent that you can remove both pans with the transmission in the car. If only Oldsmobile had stuck with that wisdom for the following 40+ years.