I cannot say for sure on the JK but on the TJ Dana 44 axle the break point on the carriers was 3.73, if you wanted to fit ratios lower then 3.73 you had to change the carrier. The TJ Dana 30 break point was 3.54 so to fit a lower ratio then 3.54 you needed to change the carrier.
Hope that is of some help.
Hope that is of some help.