The "Columbia" overdrive rear axle was available on Ford, Lincoln etc. pre-war. It replaced the right side of the differential with a new housing and an overdrive sun and planet gear set operated by a vacuum piston. It's called a 2-speed, but this isn't accurate because the differential operates normally (no extra parts engaged) unless the overdrive set is selected (which can be in any gear, giving 6 with a 3-speed etc.).
The ratios were standard and overdrive, but I can't identify the exact ratio.
