There are 1000s of diffs because the "carrier" is the same across explorers, Lincoln's, etc etc just the gear set is different. It's was more difficult to find 2.77 ratio. PP sho is quite a bit easier 3.16 ratio. It wasn't worth touching the old 1 as I suspect the gears are fine but new bearings would quickly surpass $100 and tack on labor so triple $ of another uses diff.