Postby OldGreen » Mon Nov 26, 2012 12:20 pm
Well, I have a theory:
JK D30 Ring and Pinion sets typically break because a u-joint gives up while under a load. The resultant shock load travels back through the axle shaft, which has become a torsion spring and strips the teeth off of the gears. Pretty common knowledge.
My part is that I think that the JK's built in traction control somehow exacerbates the problem by applying braking force to try and slow down a spinning wheel. . .that can break the u-joint and start the chain of events outlined above. JK Axles are also wider and probably have more flex issues than any of the older housings. None of that helps. The really weird thing is that people don't report a lot of issues with 760X/297X u-joints up to 35" tires. I absolutely ABUSED them in my CJ with 35" tires and a V8 with zero failures. Now, the JK comes along and blows that theory. . .wonder why?
As to your question, the biggest variable that you have to consider about your time bomb, in my opinion, is driving style. Since you are wearing your interwebz armor, I'll be quick to point out that you are rather timid or cautious behind the wheel. That is NOT an insult. In this case, it is a huge compliment. Your front end will probably last a good long while. I would certainly keep a set of spares on board (I do), but the second you consider beefing up the D30 with alloy axles, trusses and such, I'd take a hard look at an HP44 from our friends at Ford along with the proper bracket kit and a new set of wheels (for a different bolt pattern). You have the same u-joint, but you would be less likely to rip the ears off of the shafts, the inner shafts are bigger, and the differential set up is quite a bit stronger.
Now, If I were you, I would just stay out of the rocks and keep a spare set of shafts on board. At the MOST extreme, you could toss in an XJ front end geared to match for the HP diff, but the gear set up would be cost prohibitive. If you decide to add a locker and grow a huge right foot, then an upgrade would be in order. . .If you are just throwing in a locker, I'd keep the 30 and see how it works out. If I remember correctly, you are running 4.88 gears. That makes the locker equation a little more marginal because of the small pinion gear.
Every other Jeep site in the World would probably tell you to either throw a couple of grand at your D30 or "Go 60s and forget about it". . .but they don't wheel like we wheel and, they spend too much time on the internet and not enough out on the trail. It is SUPER easy to spend someone else's money.
Keep the 30, drive like you own it rather than like you stole it, and save your money for fuel so you can wheel more often.
