There is no question we have run our Jeep JK through some really extreme trails and over every type of terrain. We are extremely happy with how the new vehicle has held up and haven't had any issues or problems with the JK's axles or differentials. This was a concern of ours since they were all-new designs, and usually it takes some time to work the bugs out.
The only real issue we've had with the vehicle is that we've been rolling around with oversize tires and factory gearing. As you know, this lethal combo has a negative impact on overall vehicle performance. One reason we had to wait so long is that no new gearing was available due to the JK's new design.
When Mike Denton Jr. of Superior Axle & Gear called us and said "Hey guys, I have some gears for you," we jumped out of our chairs and ran down to the shop. Finally! A set of 4.88s to offset the 35-inch Pro Comps. The Superior gears that are now available for the JK include 4.88 and 5.13 Dana 44 rear (standard on all models), Dana 30 reverse-rotation front (standard on non-Rubicon models), and Dana 44 reverse-rotation front (standard on Rubicon models).
It almost goes without saying that we aren't uneasy about using Superior gears and axles; after all, the company has over 65 years of manufacturing experience. Superior manufactures all of its products under the industry's highest standards.
We are impressed with Jeep's...
We are impressed with Jeep's design of the JK's new axles. The Rubicon version of the JK's ring-and-pinion is as beefy as the Dana 60. The JK pinion shaft (center) measures in at 1.312 inches on the outer bearing race and 1.625 inches on the inner bearing race. The Dana 60 pinion shaft measures in at 1.250 inches on the outer bearing race and 1.625 inches on the inner bearing race. Though pinions usually fail at the teeth, the larger girth of the shaft certainly lends a higher degree of overall strength and dependability under harsh conditions. Pictured above are a Dana 60 (5.11) (left), JK 44 (4.88) (center), and a TJ Dana 44 (right).
Just as a comparison, here...
Just as a comparison, here are the differences in the ring gears' sizes. On the left is a Dana 60, center is a JK Dana 44, and right a JK (Sahara model) Dana 30. This should give you some idea of what axles you may need under your Wrangler based on your intended usage. Some Dana 60 axle conversions are available for the JK.
If you haven't seen the new...
If you haven't seen the new locker in the JK's Dana 44, here it is removed from the rear axle of our Jeep. Note the electrical-actuation connection plug, which is a nice upgrade from previous models.