1. An open differential means that the carrier houses the factory spider gears that allow the tires to rotate at different speeds. If it were a locked differential, the tires would rotate at the same speed. When changing gear ratios, you must match up the gearset with the appropriate carrier. For our Dana axle combo this means keeping the factory 4.10 carrier since we are swapping to a numerically higher 4.88 gear ratio. If we were to swap to a lower numerical ratio, such as a 3.55, we would need a carrier that accommodates the lower ratio.