CBJeeper

I have a Rzeppa joint failing on my JKUR front driveshaft and am researching alternatives. My question is this: If I switch to a double Cardon shaft in the front, I cannot rotate the axle to provide for proper input alignment. Why is this seldom/never addressed? Do the DC shafts operate without fail even when not setup correctly? I looked at the TF Rzeppa joint kit as an improvement but would rather replace broken u-joints on the trail then be faced with a failed Rzeppa. Thoughts?

karls10jk

You won't be faced with a rzeppa problem on the trail. You're more likely to twist the shaft and crunch that tubing. I made a choice that not many would- I put the TF rzeppa on both ends of my rear ds (2dr with 2.5") because I got a really good deal on the kit and I figured why not. So I don't need to address the rotation, but I'm aware that the actual shaft is the weak point in my system.

resharp001

Normally the DC drive shaft becomes an issue when running too high of caster on a factory axle, at which point you get some bad drive line vibes. If you're running too low caster you're actually accommodating your DS a bit more. Are you implying you have no caster correction by your comment that you can't rotate your axle? If that is the case, then you have lower than factory caster on 2" lift and you should be fine if you wanted to switch. Most us modified guys are in that 4-5* caster range. You start creeping over that on a factory axle and it gets to be a very thin line you're treading of nice driving vs. drive line vibes.

CBJeeper

I have Core 4x4 Tier 3 adjustable lowers up front so I can make caster what works best. I thought that the DC shafts needed to have the yoke rotated up to match the angle of the shaft for proper operation.

nthinuf

Caster and Pinion Angle are affected at the same time when that front axle housing is rotated. Unless you chop and re-weld the housing, can't change one without changing the other:
Raising the caster (better steering) = lowering the pinion (progressively steeper driveshaft angles)
Lowering the caster (worse steering) = raising the pinion (better driveshaft angles)

When you installed the lift, the housing rotated - so the caster was lowered and the pinion was raised a bit. Post-lift, many of us then want to raise the caster back up to improve the steering, which can put us in the position of worse pinion angles. On taller lifts, it becomes a balance between good caster and good pinion. At 2", probably won't be an issue, BUT, what is your caster set at?

resharp001

You're going to be perfectly fine. As long as long as your pinion angle has over a 1* upward bias to it on factory axle your fine. If you don't understand the caster/pinion relationship nuthinuf laid out above, you can trust us, you're caster is not over 5* with a 2" lift and new fixed length lower arms. A DC drive shaft will work for you. Be warned, even if you buy a DS with solid u-joints that you don't have to grease (which always sounds attractive), there is still a zerk in the DC portion you have to hit from time to time, and it means dropping the DS from the TC side to access it every now and then or else it will dry out over time and die just like anything else. womp womp.

CBJeeper

I installed the lower adjustable control arms, lengthened them to 23"(from memory) and the handling was much improved. I have yet to get in to the shop for alignment and caster. What should I suggest to the technician for caster? 2 degrees positive?

nthinuf

Factory spec for caster is 4.2* ( +/- .5* ). So 3.7 - 4.7 according to the engineers. After a lift, many like to be up closer to 5*. Since you have adjustables, you can try a few experimental adjustments and see what you think. Or since it sounds like you are happy with the caster now, go find a place that will print the 'before' specs for free just to see where you're at - and leave it alone.

CBJeeper

Excellent, will do. I appreciate all of the advice. This puts me on the path of putting my money on a new DC shaft with 1310's. I like the line of logic that the u-joints be the weak link.