What is a carrier break? Does this mean that regearing would be useless if I get a locker (I'd like to get 4:56 gears)? Just curious...
A "carrier break" refers to an axle using a different carrier/locker for different gear ratios.
The "carrier" is what the ring gear bolts to. Its the locker if you have a full case locker (ARB, Detroit, Ox, etc.).
Your D30 has a carrier break at 3.55/3.73 meaning that the axle uses the same carrier/locker for 3.73, 4.10, 4.56, or 4.88. 3.55 or anything numerically lower requires a different carrier/locker.
Your D44 has a carrier break at 3.73/3.92. So 3.92, 4.10, 4.27, 4.56, 4.88, etc. all use the same carrier/locker.
To add to the confusion, there are "thick gears" available for your D44. Thick gears allow you to use the numerically lower gear ratios (3.73, 3.55, 3.27, etc.) on the 3.92 and numerically higher carrier/locker.