[Warrant]

I’m wondering if I’ll have to go with aftermarket driveshafts with 4” Currie springs and a “medium” tummy tuck? (UCF “extra clearance” skid, it’s about 2” below the frame rails) on a 06 LJ Rubicon? Already have the 4” springs and full adjustable arms all around and planning on using their low profile transmission mount as well.

What have others experiences been? And which drivehaft usually needs to be replaced for issues? The rear since it’s not a double cardon?

 

[inline6]

It would be the rear

I would give it a shot and see what happens.

 

[stangmata]

Expect to need a new rear DS. I have about 3.5” lift and a savvy TT and I had horrible vibrations from the rear DS.

 

[elff]

Absolutely will need a rear. Front will be fine.

 

[DAA]

Should be fine with the factory rear drive shaft. I've run the factory shaft for 150K miles now. With 3" springs, but a higher belly skid - sounds like probably very close to the same angles you will have with 4" springs and the UCF skid.

Just remember that pinion angle with the factory shaft needs to be equal and opposite of the output. Which will mean adjusting the pinion a bit lower. Opposite of running a CV shaft where the pinion needs adjusted up to point straight at the output.

- DAA

 

[Elwarpo]

Since this is a LJ with a longer shaft, you are at the edge of vibes. Front is already double CV and will be good, Single CV rear is a bit shorter than the front. Adjusting the rear pinion with your upper control arms will help a lot. A MML will also help. I would guess you will be OK without a new shaft, but you will be close. I am running a LJ with a similar setup 3 1/2" lift and TT and am using the stock drive shafe, but I have a Clayton LA with triangulated rear, so not the same thing.

 

[Elwarpo]

Expect to need a new rear DS. I have about 3.5” lift and a savvy TT and I had horrible vibrations from the rear DS.

TJ or LJ?

 

[stangmata]

LJ

 

[harvinjeep]

Mine is a similar set up on the Clayton long arm, but with 4" springs. A 1 in MML and 1.25BL, but it took a new rear shaft. My front one was replaced at the same time, I would have to go back and look at notes but I remember it being off from where I wanted the length to be on it, but don't remember how much off the top of my head.

 

[leroymax45]

I'm not as familiar with your model, but my TJ required rear DS to have slip yoke and dwell angle of rear diff adjusted. Now theres no vibration until u-joints fails, which happens every 10 - 15k miles. There is a grease fitting in the u-joint that requires a special tip on grease gun. Its a pain to lube and fails every 10-15k miles either way, whether lubed, or not.

 

[elff]

It requires that needle tip.
Even though I have one, and I do grease them, I am never really sure If I get any grease into that section.
It's a pita. I think your statement is very accurate. LOL

 

[Elwarpo]

On a TJ 4" is the majic Number, 6" for a LJ like you. This is a combination of lift and TT. The issue with a LJ is the front and rear DS is about the same length so at 6" you may need a new DS. A MML/BL will help, and so would upper adjustable control arms to readjust pinion angle. You are in the area where the only real answer is it may. I rub 4" springs and a 2" TT on my red LJ and with adjustable UCAs/MML I have the stock DS. In my other LJ with a bit more lift I have a double CV driveshaft.

 

[Norminator]

I finally grew out of my stock rear driveshaft recently over the drip drip drip pace of mods. I reached a combined mod challenge to my rear driveshaft and began wondering as you are. You’ll be encouraged to know that the answer to your question is pure math and science. I had eavesdropped on a lot of driveline vibe discussions on this forum, but didn’t grasp it until I watched a lot of YouTube and particularly the Tom Wood ones. Your driveline angle will be what it will be. Get a digital angle measure that you can set to zero. There are good videos out there on where to measure. Get your baseline angles before anymore changes. You will then know exactly how much wiggle room you have. I myself struggled with wrapping my brain around the principles, but it finally clicked.

My vibration was actually so small I couldn’t tell if it was the driveline or just tires and road. I figured for complete knowledge I’d pull the rear driveshaft and drive around on the front. That made it clear I did indeed have vibration. At that point I decided to move forward with a double cardan shaft and adjustable rear uppers. My stock driveshaft was at least twenty years old and pushed hard. I wanted to repeat that.

I’ll see if I can make a video. I’m a driveline rookie, but maybe that will help me articulate it for newcomers to the subject. It’s going to take me a few days.