Empire Strikes Back commentary track had this info .

C-3P0’s walking sounds were made with the window motor of an old Chrysler.

The snow speeders flying is the LA highway recorded through a vacuum cleaner tube.

https://www.facebook.com/Questionposting/posts/pfbid0rFWUw9fEemCyLfaQApz8Bcyf4cELyB5oJ8eYdbMXfgrzaUehe6WhEbDQd4mw5GyBl