they didn't make an 01 fx4. But in 02 they did, and the torsen on those the early models were notorious for blowing out, so i bet that is what happened. But yes, any 31 spline carrier would work for your 8.8.
lol that you counted. it is really difficult to do, espically when you end up with 29 or 30 and you're sure you got them all....i tried once....