When swapping gears from 3.55s or higher (3.07s, etc) to 3.73s or lower (4.10s, 4.56s, etc) you will need a low ratio carrier in addition to the ring & pinion. This is an OE-quality carrier built with the same quality control standards as original equipment parts.
This is a genuine Dana Spicer carrier and is sold bare; the side and spider gears from the original carrier can be used with this new carrier.