Thanks for the information. The Ford website doesn't seem to make the distinction between different 8.8 ring gears. The only thing I noticed was that the ones that were advertised as a super 8.8 ring gear, had the letter A at the end of the part number. Knowing that there was a 3.31 option in 2015 models, it through me off because there were different part numbers for the 3.55 but not the 3.31 gears. Maybe it's because they never made a 3.31 for early models? In case you are interested m4209-88355 vs m4209-88355A.