Understanding Gearing Ratios for the 6R80

I am trying to find the gearing ratios for the mustang automatic transmission with 3.55 gearing. Are the gearing ratios the same between the 3.15 and 3.55? How does the 3.55 have better acceleration if the ratios are the same as the 3.15? Sorry for the newb question, just trying to get a better understanding.


Gear ratios

First 4.17
Second 2.34
Third 1.52
Fourth 1.14
Fifth 0.87
Sixth 0.69

Final drive
3.15:1, 3.55:1 (optional)

The 6R80's gearing is the same regardless of what the final drive is, but the final drive applies to all of those ratios. It's essentially separate from the transmission and located in the rear end and acts like a multiplier/reducer... I don't know the best way to explain it.

This picture does a decent job of explaining things. Same forward ratios with two separate final drives. Notice that the lower the axle ratio (higher numerical value) shortens the overall gearing spread, leading to theoretically quicker acceleration with a sacrifice in potential top speed (provided things like drag and power limitations aren't a factor).