Unless the whole rear end assembly has been changed, find the rpo sticker, should be in either glove box or center console. GU2= 2.73
GU4=3.23 GU6=3.42
2.73 gears use the series 2 carrier and needs to get gears for a series 2 carrier.
3.23 & 3.42 use a series 3 carrier and must use gears for a series 3 carrier.