Upgrading the axles isn’t the only reason to be cracking into the rear differential assembly. Many Challenger owners are going to crack into the housing to make upgrades to the differential carrier and ring gear. This begs the question of “can you build your differential to a point where the axles should be upgraded?”
Differential Type: The differential in a Challenger is usually a limited-slip unit. Very few who drive the car daily will want to change this unless it’s time to service the unit. Serious drag racers will want to spend the time to install a spool or locker differential to the car for better acceleration. With that in mind, we suggest upgrading the axles when moving to a spool because these units are designed to provide maximum traction to both axles at all times.
Ring Gear: When upgrading the ring and pinion you will be left asking yourself the same question. With enough power and the factory ring gear, launching on factory axles is already dodgy. Using lower ring gear will have the tires up to speed quicker will also mean those forces are applied to the axles faster as well making it well worth considering upgrading the axles with the use of a lower ring gear.
While You’re at It: Dealing with a broken axle is not a good situation. Even if it doesn’t happen on the spot, forces can create cracks in the axle that won’t result in the axle giving up until a later date. If you are already dumping money into a new set of ring and pinion gears and a new carrier you might as well invest in a set of strong axles. There is no such thing as having too strong of axle shafts.