A while back, I posted photos of the insides of a Model 15 transaxle. More recently, I purchased a second Model 20. It made an awful noise when I moved it around, so today I opened up the Gear Case. Given the lack of oil, surplus of rust, and number of chipped teeth, I am surprised it even moved. Didn't find the chips, though.
Oh, and I have also recently found a parts manual for the 20. They call it a Gear Case, not a transaxle. Hence the name change.