U-Joint Selection

[inVERt'D]

It's how you massage that skinny pedal!

I'm wid dat. Sometimes a little momentum can make up for a lot of torque, too.

[Elusive]

I'll throw out some observations:
1. I don't buy into the "create a weak link" principal. Build your axles with the strongest parts available. The shock loads transmitted through the axle when a part breaks it hell on every part of your drivetrain. Let me give you an example. I was wheeling with an experienced jeeper when his front left chromolly axleshaft snapped. In less than half a second, the torque that was being applied to BOTH the front wheels now went 100% to the right front wheel and the locker broke. Now the torque that was being delivered to all 4 wheels was transmitted 100% to the rear axle and the rear driveshaft snapped. This sounds like the guy just stayed in the throttle till it all came apart, but it all happened in a fraction of a second.
2. When the U-joints break, it usually damages the axle shafts.
3. Axle shafts almost never break in the middle, flanged axle always break at the splines and U-joint axles break either at the splines or at the yoke. Changing a rear axle on the trail is a nice thought, but 90% of the time the splines are stuck in the Diff, or chunks of the shaft are floating around in the diff destroying gears and you need to pull the diff out to replace the shaft. The front axles can be swapped on the trail IF the yokes still fit through the knuckle after the U-joint explodes and IF the broken outer shaft will come out of the spindle.
4. (still reading?) Your jeep came with spicer 760 joints in the axles. These are the strongest OEM joints ever made. If you keep the wheel straight when you are on the gas, you'll never snap a joint. The absolute worst thing you can do is nose down, crank the wheel, and try to reverse out of something. If you don't do that, you'll keep your front axle happy for a long time on 35's.

[inVERt'D]

Whatever you do as far as u-joints, it would be a good idea to make sure they're well lubed before hitting something like the Rubicon. No, your 760Xs don't have zerk fittings, because a hollow u-joint is a weaker u-joint (I do like the zerk caps in the Alloy USA X-Joints). You can use a needle attachment for your grease gun to get under the caps, but it's good practice to tear down and inspect the joints from time to time. I think a lot of u-joints fail on the trail because people don't bother to maintain them at home.

Tear-down/ inspection means you have to pull and disassemble your front axles. Yeah, it's kind of a pain in the butt, but it's a lot nicer at home and it's a good drill for the trail. If they're not significantly worn, you can regrease them, or grease up some new ones. Compared to the time you'll spend doing it, new 760Xs are pretty cheap. You can keep the old ones for spares. Careful you don't lose the needle bearings; if they're dry they tend to jump out.

By the way, using a socket to drive out stubborn caps sucks. If it's the only way you have to do it then by all means, but there are better ways. If you're at home and have a bench vice, open it up just enough to put the ears/sides of your yoke on either jaw. One side of the yoke should now be facing up. Take an impact hammer and strike the yoke right on the "chin," where it's fairly thick. This will drive out even caps that are rusted in.

Here's an article on the Spicer 760Xs.

http://www.4wheeloffroad.com/product...eps/index.html

[blackZZR]

2cents time

I have seen a lot of damage done to diffs and driveshafts because people ran those unbreakable universal joints. Definately need that thing to fuse the system. A under 20 dollar spicer u joint is a strong unit, but still goes before a driveshaft twist up like a cops breakfast.
Being a big fan of the D30, D44 combo and running my Jeep all over the west, I think a short course in right foot control, the ability to admit when you are stuck and a decent set of axles saves thousands over expensive over builds and broken parts.
Now that said, my jeep mainly sees trail duty, I carry 2 ujoints as spares, and change out all of the ones under the jeep every other season.
But then I am a tight wad who does not want to pay for new axles and stuff, so I happily use the ones I have not breaking them.

[RAT]

Using the u-joint as the "fuse" sounds good in principle, but a broken u-joint will very easily result in a broken or tweaked yoke. Your Rubicon came with Dana Spicer 760x u-joints, which are an stronger upgrade to (and swapable with) 297s. Alloy USA makes a reasonably inexpensive forged steel alloy version I've seen on eBay for under $40 ea.; "X-Joint" p/n 11500.

I can vouch for these Ujoints (alloys)as I have been through several sets, which Alloy promptly replaced at no charge. I've not had a catastrophic failure, just needle bearings wearing out very fast. But when a Ujoint goes, if it goes hard, the ears on the inner and outer shafts can get tweaked real bad and might be damn hard, if not impossible to remove on the trail. Andrew can attest to that little bit of fun. So a spare set of axles is always a plus. I just took a D44 front apart to remove the Jeep Locker and add an ARB. It looks to me to be a pretty stout peice, but I'm guessing if it breaks, it will be at the bearing journals. It seems to be a bit thin there.

[Ol Man]

CTMs. You will not break them. You must run alloy axles to use them.

[Double AA]

But when a Ujoint goes, if it goes hard, the ears on the inner and outer shafts can get tweaked real bad and might be damn hard, if not impossible to remove on the trail. Andrew can attest to that little bit of fun.

If the ears spread just a few thousands they can be a real bear to pull through the knuckle, and turn a 30 minute repair into something much longer.

If you have locking hubs and you break (well maintained) U joints with and kind of regularity, don't replace them with anything but 300M. Longfield's or CTM's, one's as strong as the other.

It's hard to justify the price until a broken U joint causes an axle shaft or differential to break.

[dirtman13]

(I do like the zerk caps in the Alloy USA X-Joints).

x2 on the X-joint.

Now I break hubs which is easier to replace on the trail...and more expensive. But better then the axle itself.