iv been messing with some over last week or 2 even thou you got it soaking take a small brass brush pull the part out and lightly brush it you will see a film come right off
may be a couple spots size of a corn flake that may need some extra soaking
iv learned you have to have the whole part submerged as i had a tail shaft housing off a 4 speed and had enuff to cover half way up (laying down) well you cant roll it over and do the other side but the side that was in worked very good as this thing looked like its been outside in the weather for years lol